ALLAMA IQBAL OPEN UNIVERSITY, ISLAMABAD (Department of Computer Science) Course: Computer Architecture (3416) Level: BS (CS) Semester: Spring, 2011 Total Marks: 100 ASSIGNMENT No. 1 All questions carry equal marks. Q.1 a) Explain block diagram of computer state your answer with the help of a neat diagram? Input Unit: Computers need to receive data and instruction in order to solve any problem. Therefore we need to input the data and instructions into the computers. The input unit consists of one or more input devices. Keyboard is the one of the most commonly used input device. Other commonly used input devices are the mouse, floppy disk drive, magnetic tape, etc. All the input devices perform the following functions. Accept the data and instructions from the outside world. Convert it to a form that the computer can understand. Supply the converted data to the computer system for further processing. Storage Unit: The storage unit of the computer holds data and instructions that are entered through the input unit, before they are processed. It preserves the intermediate and final results before these are sent to the output devices. It also saves the data for the later use. The various storage devices of a computer system are divided into two categories. 1. Primary Storage: Stores and provides very fast. This memory is generally used to hold the program being currently executed in the computer, the data being received from the input unit, the intermediate and final results of the program. The primary memory is temporary in nature. The data is lost, when the computer is switched off. In order to store the data permanently, the data has to be transferred to the secondary memory. The cost of the primary storage is more compared to the secondary storage. Therefore most computers have limited primary storage capacity. 2. Secondary Storage: Secondary storage is used like an archive. It stores several programs, documents, data bases etc. The programs that you run on the computer are first transferred to the primary memory before it is actually run. Whenever the results are saved, again they get stored in the secondary memory. The secondary memory is slower and cheaper than the primary memory. Some of the commonly used secondary memory devices are Hard disk, CD, etc., Memory Size: All digital computers use the binary system, i.e. 0’s and 1’s. Each character or a number is represented by an 8 bit code. The set of 8 bits is called a byte. A character occupies 1 byte space. A numeric occupies 2 byte space. Byte is the space occupied in the memory. etc and does logic operations viz. 80286. The control unit is generally referred as the central nervous system of the computer that control and synchronizes its working. 256MB memory are quite common. The size of the primary storage in a typical PC usually starts at 16MB. Pentium III. Control Unit: It controls all other units in the computer. >. 80486. Output Unit: The output unit of a computer provides the information and results of a computation to outside world.The size of the primary storage is specified in KB (Kilobytes) or MB (Megabyte). ‘etc. Pentium. Visual Display Unit (VDU) are the commonly used output devices. It also controls the flow of results from the ALU to the storage unit. Celeron. Other commonly used output devices are floppy disk drive. where to store the data after receiving it from the user. division. 128 MB. It controls the flow of data and instructions from the storage unit to ALU. PCs having 32 MB. the control unit transfers the data from storage unit to ALU once the computations are done. and AMD etc. • It takes all decisions. Arithmetic Logical Unit: All calculations are performed in the Arithmetic Logic Unit (ALU) of the computer. The CPU is like brain performs the following functions: • It performs all calculations. The ALU can perform basic operations such as addition. • It controls all units of the computer. subtraction. =. Central Processing Unit: The control unit and ALU of the computer are together known as the Central Processing Unit (CPU). 48MB. <. the results are transferred to the storage unit by the control unit and then it is send to the output unit for displaying results. Pentium Pro. Pentium IV. Whenever calculations are required. Pentium II. hard disk drive. One KB is equal to 1024 bytes and one MB is equal to 1000KB. Printers. The control unit instructs the input unit. multiplication. and magnetic tape drive. 80386. A PC may have CPU-IC such as Intel 8088. It also does comparison and takes decision. Dual Core. . and output was displayed on printouts. High-level programming languages were also being developed at this time. cheaper. users interacted with third generation computers through keyboards and monitors and interfaced with an operating system. developed in 1971. These were also the first computers that stored their instructions in their memory. such as early versions of COBOL and FORTRAN. Input was based on punched cards and paper tape. and in 1984 Apple introduced the Macintosh. Census Bureau in 1951. it was a vast improvement over the vacuum tube. to perform operations. more energyefficient and more reliable than their first-generation predecessors. Instead of punched cards and printouts.b) Explain different generations of computers by identifying the main improvement in each generation? First Generation (1940-1956) Vacuum Tubes The first computers used vacuum tubes for circuitry and magnetic drums for memory. The transistor was invented in 1947 but did not see widespread use in computers until the late 1950s. which drastically increased the speed and efficiency of computers. The UNIVAC and ENIAC computers are examples of first-generation computing devices. The first computers of this generation were developed for the atomic energy industry. taking up entire rooms. which moved from a magnetic drum to magnetic core technology. Computers for the first time became accessible to a mass audience because they were smaller and cheaper than their predecessors. languages. Third Generation (1964-1971) Integrated Circuits The development of the integrated circuit was the hallmark of the third generation of computers. Second-generation computers moved from cryptic binary machine language to symbolic. called semiconductors. Second-generation computers still relied on punched cards for input and printouts for output. or assembly. Transistors were miniaturized and placed on silicon chips. Microprocessors also moved out of the . which was often the cause of malfunctions. as thousands of integrated circuits were built onto a single silicon chip. The Intel 4004 chip. which allowed programmers to specify instructions in words. the U. which allowed the device to run many different applications at one time with a central program that monitored the memory. The UNIVAC was the first commercial computer delivered to a business client.S. They were very expensive to operate and in addition to using a great deal of electricity. located all the components of the computer—from the central processing unit and memory to input/output controls—on a single chip. Though the transistor still generated a great deal of heat that subjected the computer to damage. faster. generated a lot of heat. Second Generation (1956-1963) Transistors Transistors replaced vacuum tubes and ushered in the second generation of computers. and were often enormous. Fourth Generation (1971-Present) Microprocessors The microprocessor brought the fourth generation of computers. In 1981 IBM introduced its first computer for the home user. the lowest-level programming language understood by computers. allowing computers to become smaller. First generation computers relied on machine language. and they could only solve one problem at a time. What in the first generation filled an entire room could now fit in the palm of the hand. The transistor was far superior to the vacuum tube. based on artificial intelligence. The goal of fifth-generation computing is to develop devices that respond to natural language input and are capable of learning and selforganization. . which eventually led to the development of the Internet. The use of parallel processing and superconductors is helping to make artificial intelligence a reality. the mouse and handheld devices. though there are some applications. Fourth generation computers also saw the development of GUIs. As these small computers became more powerful.realm of desktop computers and into many areas of life as more and more everyday products began to use microprocessors. are still in development. that are being used today. Quantum computation and molecular and nanotechnology will radically change the face of computers in years to come. such as voice recognition. they could be linked together to form networks. Fifth Generation (Present and Beyond) Artificial Intelligence Fifth generation computing devices. You can also use a CD drive to play music CDs on your computer. Another component israndom access memory (RAM). the typical mouse does look a bit like an actual mouse. The cables plug into specific ports (openings). Usually it's a rectangular box placed on or underneath your desk. If you have a recordable disk drive. The disk preserves the information even when your computer is turned off. Applies to all editions of Windows Vista. Almost every other part of your computer connects to the system unit using cables. Storage Your computer has one or more disk drives—devices that store information on a metal or plastic disk. The most important of these components is the central processing unit (CPU). CD and DVD drives Nearly all computers today come equipped with a CD or DVD drive. It's small. Mouse A mouse is a small device used to point to and select items on your computer screen. The information stored in RAM is erased when the computer is turned off. you can store copies of your files on blank CDs. Although mice come in many shapes. and many CD drives can also write (record) data onto CDs. Hard disk drive Your computer's hard disk drive stores information on a hard disk. Because hard disks can hold massive amounts of information. oblong. which temporarily stores information that the CPU uses while the computer is on. System unit The system unit is the core of a computer system. usually located on the front of the system unit. they usually serve as your computer's primary means of storage. CD drives use lasers to read (retrieve) data from a CD.2 a) What are different component of computer? Also explain functions associated with each component. a rigid platter or stack of platters with a magnetic surface. Some newer mice are wireless.Q. typically on the back of the system unit. Inside this box are many electronic components that process information. Hardware that is not part of the system unit is sometimes called a peripheral device ordevice. or microprocessor. Compare editions . The hard disk drive is normally located inside the system unit. holding almost all of your programs and files. and connected to the system unit by a long wire that resembles a tail. which acts as the "brain" of your computer. refers to the instructions. that tell the hardware what to do. you might already know that there isn't any single part called the "computer. A laptop computer has similar parts but combines them into a single notebook-sized package. . but it probably has most of these parts. (Software. are collectively called hardware." A computer is really a system of many parts working together.In this topic • System unit • Storage • Mouse • Keyboard • Monitor • Printer • Speakers • Modem See also • Introduction to computers • Using your mouse • Using your keyboard • Windows Basics: all topics Parts of a computer If you use a desktop computer.) The illustration below shows the most common hardware in a desktop computer system. or programs. which you can see and touch. Your system may look a little different. on the other hand. The physical parts. CD drives use lasers to read (retrieve) . Because hard disks can hold massive amounts of information. usually located on the front of the system unit. Hard disk drive Your computer's hard disk drive stores information on a hard disk. The most important of these components is the central processing unit (CPU). CD and DVD drives Nearly all computers today come equipped with a CD or DVD drive. The cables plug into specific ports (openings). The disk preserves the information even when your computer is turned off. Inside this box are many electronic components that process information. Storage Your computer has one or more disk drives—devices that store information on a metal or plastic disk. Hardware that is not part of the system unit is sometimes called a peripheral device ordevice. which temporarily stores information that the CPU uses while the computer is on. typically on the back of the system unit. which acts as the "brain" of your computer.Desktop computer system Let's take a look at each of these parts. The hard disk drive is normally located inside the system unit. Usually it's a rectangular box placed on or underneath your desk. or microprocessor. Another component is random access memory (RAM). System unit The system unit is the core of a computer system. a rigid platter or stack of platters with a magnetic surface. they usually serve as your computer's primary means of storage. Almost every other part of your computer connects to the system unit using cables. holding almost all of your programs and files. The information stored in RAM is erased when the computer is turned off. Many mice also have a wheel between the two buttons. Compared to CDs and DVDs. that's just the sleeve. Like the keyboard on a typewriter. a pointer on your screen moves in the same direction. . DVD drives can do everything that CD drives can. • The numeric keypad.) When you want to select an item. allows you to enter numbers quickly. For more information. it has keys for letters and numbers. When you move the mouse with your hand. the typical mouse does look a bit like an actual mouse. and many CD drives can also write (record) data onto CDs. Although mice come in many shapes. Floppy disk drive Floppy disk drives store information on floppy disks. floppy disks can store only a small amount of data. floppy disk drives are less popular than they used to be. For these reasons. although some computers still include them. allow you to move your position within a document or webpage. flexible vinyl material. Some newer mice are wireless. perform different functions depending on where they are used. see Using your mouse. It's small. T Mouse A mouse is a small device used to point to and select items on your computer screen. you point to the item and then click (press and release) the primary button. A mouse usually has two buttons: a primary button (usually the left button) and a secondary button. plus read DVDs. found on the top row. also called floppies or diskettes. The disk inside is made of a thin. Many DVD drives can record data onto blank DVDs. you can store copies of your files on blank CDs. but it also has special keys: • The function keys. which allows you to scroll smoothly through screens of information. such as the arrow keys. located on the right side of most keyboards. • The navigation keys. If you have a DVD drive. Keyboard A keyboard is used mainly for typing text into your computer. and connected to the system unit by a long wire that resembles a tail. If you have a recordable disk drive. Pointing and clicking with your mouse is the main way to interact with your computer. you can watch movies on your computer.data from a CD. Why are floppy disks "floppy"? Even though the outside is made of hard plastic. They also retrieve information more slowly and are more prone to damage. oblong. You can also use a CD drive to play music CDs on your computer. (The pointer's appearance might change depending on where it's positioned on your screen. The portion of the monitor that displays the information is called the screen. however. Ram Random access memory. . such as printers. using text and graphics. There are two basic types of monitors: CRT (cathode ray tube) monitors and LCD (liquid crystal display) monitors. CRT monitors. are generally more affordable. a computer screen can show still or moving pictures. any byte of memory can be accessed without touching the preceding bytes. Like a television screen.Monitor A monitor displays information in visual form. but LCD monitors have the advantage of being much thinner and lighter. that is. RAM is the most common type of memory found in computers and other devices. Both types produce sharp images. a type of computer memory that can be accessed randomly. Address Bus: The address bus consists of all the signals necessary to define any of the possible memory address locations within the computer. and so forth) necessary to control and coordinate the operations of the computer. interrupt. Before data or instructions can be written into or read from memory by the CPU or I/O sections. There are three types of buses They are: Control Bus: The control bus is used by the CPU to direct and monitor the actions of the other functional areas of the computer. symbol. The information on the data bus is either written into memory at the address defined by the address bus or consists of data read from the memory address specified by the address bus.b) What is meant by a bus? Explain different types of buses used in computer. A bus is two or many wire communication method. & control signals. An address is defined as a label. It is used to transmit a variety of individual signals (read. write. an address must be transmitted to memory over the address bus. . or for modular memories any of the possible memory address locations within a module. It carries data (operands) to and from the CPU and memory as required by instruction translation. or other set of characters used to designate a location or register where information is stored. it may transfer address. address. handles the transfer of all data and instructions between functional areas of the computer. Buses are the set of wires that carry special information to or from the cpu. The data bus is used to transfer instructions from memory to the CPU for execution. The individual signals transmitted over the control bus and their functions are covered in the appropriate functional area description. Data Bus: The bidirectional data bus. A bus which communicates between two active devices. BUS: A bus is a group of conducting lines that carrier’s data. The data bus is also used to transfer data between memory and the I/O section during input/output operations. etc. acknowledge. The bidirectional data bus can only transmit in one direction at a time. data. sometimes called the memory bus. but such a design requires a separate DMA controller for each device. Direct Memory Access (DMA): . When the operating system starts running. The operating system can only use DMA if the hardware has a DMA controller. and decrementing the count of items to be read until it reaches zero. DMA can begin. often concurrently. The write to memory is another standard bus cycle. with each iteration reading one byte or word from a controller device register. and the number of bytes to transfer in one burst. No matter where it is physically located.) It also issues a command to the disk controller telling it to read data from the disk into its internal buffer and verify the checksum. and the disk controller does not know or care whether it came from the CPU or from a DMA controller. Typically. called DMA (Direct Memory Access) is often used. it computes the checksum to verify that no read errors have occurred.g. the transfer unit (byte at a time or word at a time). the memory address to write to is on the address lines of the bus so when the disk controller fetches the next word from its internal buffer. it knows where to write it. a single DMA controller is available (e. The control registers specify the I/O port to use. the direction of the transfer (reading from the I/O device or writing to the I/O device). It contains several registers that can be written and read by the CPU. and one or more control registers. (Step 1 in fig.Whether or not a system has memorymapped I/O. the disk controller sends an acknowledgement signal to the disk controller. storing it in main memory. bit by bit. The DMA controller initiates the transfer by issuing a read request over the bus to the disk controller (Step 2) This read request looks like any other read request. until the entire block is in the controller’s internal buffer. its CPU needs to address the device controllers to exchange data with them. as shown in Fig. it can read the disk block from the controller’s buffer a byte or a word at a time by executing a loop. These include a memory address register. First the controller reads the block (one or more sectors) from the drive serially. (Step 3) When the write is complete. Then the controller causes an interrupt. the DMA controller has access to the system bus independent of the CPU. Sometimes this controller is integrated into disk controllers and other controllers. on the parent board) for regulating transfers to multiple devices. When DMA is used. More commonly. When valid data are in the disk controller’s buffer. incrementing the memory address.3 a) Explain the use of DMA controller in a computer system with a neat diagram. Next. which most systems do. so a different scheme. The CPU can request data from an I/O controller one byte at a time but doing so for a device like a disk that produces a large block of data wastes the CPU’s time. First the CPU programs the DMA controller by setting its registers so it knows what to transfer where. the procedure is different.. a byte count register. also over the bus .Q. If the byte count is still greater than 0. When the operating system starts up. steps 2 through 4 are repeated until the count reaches 0.(Step 4) The DMA controller then increments the memory address to use and decrements the byte count. At this point the controller causes an interrupt. it is already there. . it does not have to copy the block to memory. Both of them use floating gate transistors to which electrons are tunneled for erasing the data. cards.0. and a current of opposite polarity is induced for erasing the data whereas in the NAND type. which increases the speed of the peripheral to PC connection from 12 megabits per second (Mbps) on USB 1. In the NOR type the initial values will be 00. memory sticks. Like any other electronic gadget.1 to up to 480 Mbps on USB 2. Intel and others started to demonstrate USB 2. USB pen drives are typically portable USB flash memory devices as it is the incorporation of technology of flash memory that allows you to rewrite or erase the data stored in these devices.b) Describe the working principles of USB? The USB (for Universal Serial Bus) is a low cost serial bus which initially provided up to 12 Mb/S. That's about 100 times faster than the RS-232 style serial interfaces used in earlier generations of computers. USB pen drive and so on. The major success of the USB flash memory device lies in its increased capacity to store high amount of information together with its shock proof and dust proof nature which were the major limitation witnessed in the floppies of the earlier years. USB flash memory devices contain a collection of cells or chips and can be either NOR or NAND type flash depending upon the way it is connected. or 40 times faster than with the older technology. In June 2002. Thus these tiny devices have definitely created a revolution in the field of information technology. . The NAND flash has found its applications in digital cameras. And also flash memory is responsible for the high durability of the compact removable disk. the initial values are maintained at FF.0. or to store information in it. Magnetic Tape Storage The device that performs reading and writing of data on magnetic tapes is a tape drive. But the secondary memory is much slower and also less costly.Q. The most familiar form of secondary memory that is widely used is Hard Disk. This memory is accessed by CPU. It stores the data permanently unless it is erased. .4 a) Describe the functional characteristics that are common to build main and secondary computer memory? Primary Memory: The primary memory or the main memory is part of the main computer system. o The primary memory itself is implemented by two types of memory technologies. The first is called Random Access Memory (RAM) and the other is read only memory (ROM). Tapes can be cost effective while storing large amounts of data. Input/output channels are used to access this nonvolatile memory. Secondary Memory Characteristics: Secondary memory is not directly accessible to the CPU. DVD and Blue-ray Disc. The processor or the CPU directly stores and retrieves information from it. Today they are largely used for backups and archives. That means any location of this memory can be accessed by the CPU to either read information from it. A more appropriate name for RAM is RWM (Read Write Memory). in random fashion. floppy drives and Zip drives. There are drives that only read while on the other hand some drives are also there that performs both reading and writing. Some examples of secondary memory are USB sticks. the CPU can write and read information from any primary memory location implemented using RAM. Primary memory is much faster and also it is more cost effective. This memory does not lose the data when the system is powered off. These devices include CD. Hard Disks A Hard Disks Drive (HDD) is a nonvolatile secondary storage device which stores digitally encoded data on the magnetic surface of it. The other part of primary memory is implemented using ROM which stands for Read Only Memory. Optical Disc Storage Optical Disc Drives use electromagnetic waves or laser light to read and write information to optical discs. to make up their memories. For example. depending on the computer type. The larger mainframe computers use the modular arrangement. Core memory is an example. A semiconductor memory is an example. Whereas. Magnetic I/O Main tapes memory processor Magnetic disks CPU Cache memory Register Cache Main Memory Magnetic Disk Magnetic Tape .b) Give a brief description of computer memory organization? Volatile memories —Volatile memories are memories that lose their contents when the power is turned off. MEMORY ORGANIZATION Memory organization is two-fold. Nonvolatile memories —Nonvolatile memories are memories that do not lose their contents when power is removed. They also have a readonly memory which is usually a part of the CPU. Minis and micros use multiple components on one pcb or groups of pcb’s to form the memory. minicomputers and microcomputers use chassis or assemblies. cages or racks. Memory in a computer can vary from one or more modules to one or more pcb’s. multiple modules (four or more). they may use some type of magnetic memory (core or film) and also a semiconductor memory (static or dynamic). then the internal architecture. Some computers have a mixture of memory types. First we discuss the hardware (physical) organization. and motherboard or backplane arrangements. The type of computer and its size do not reflect the type of memories that the computer uses. The CPU then sends a read control signal. These memories can be static or dynamic. But the complexity of the architecture puts a limit on the amount of the processor memory. It can also stay in the same chip as of CPU. They store the operands and the result of an instruction. Internal on-chip Memory 3. way of data storage etc The memory at the basic level can be classified as 1. The data is stored in that location is transferred to the processor via the data lines. Processor Memory (Register Array) 2. Cache Memory 5. Primary Memory This is the one which sits just out side the CPU. . The memory can be classified in various ways i. based on the location.Q. Cache Memory This is situated in between the processor and the primary memory. The number of registers varies from processor to processor.5 a) Explain how the processor is interfaced with memory with a neat block diagram and explain how they communicate? In a memory read operation the CPU loads the address onto the address bus. power consumption. Internal on-chip Memory In some processors there may be a block of memory location. This serves as a buffer to the immediate instructions or data which the processor anticipates. Secondary Memory Processor Memory (Register Array) Most processors have some registers associated with the arithmetic logic units. The more is the number the faster is the instruction execution. In the memory write operation after the address is loaded the CPU sends the write control signal followed by the data to the requested memory location. The data transfer rates are much faster without needing any additional clock cycles. There can be more than one levels of cache memory.e. However it is very fast. Most cases these lines are fed to a decoder which selects the proper memory location. Primary Memory 4. They are treated as the same way as the external memory. They are much cheaper mass storage and slower devices connected through some input/output interface circuits. The memory can also be divided into Volatile and Non-volatile memory. . They are generally magnetic or optical memories such as Hard Disk and CDROM devices. Semiconductor Random Access Memories fall into this category. Magnetic Memories (Hard Disks). * Volatile Memory The contents are erased when the power is switched off. Read Only Memories (ROM) fall under this category.Secondary Memory These are generally treated as Input/Output devices. * Non-volatile Memory The contents are intact even of the power is switched off. Optical Disks (CDROMs). many parts of your PC if you open it up for any reason. whereas dynamic is obviously something that changes all the time. . The only connection with static electricity that I can think of. The second one is that SRAMs are also used for specific applications within the PC. For as long as power is supplied to the circuit. Other than that.b) Write a note on static memories? The Static Random Access Memory (Static RAM) is a high speed memory. is that static electricity is a real threat to extra RAM that you can plug into your PC or. Once you put a file somewhere on your hard disc. unlike dynamic memory allocation or allocation where memory is allocated as required at run-time. where their strengths outweigh their weaknesses compared to DRAM Static memory allocation refers to the process of allocating memory at compiletime before the associated program is executed. The first of all is duty to refresh memory many times per second to hold its data contents. staying the same. changes all the time. static means staying in one place. The contents of the RAM etc. it stays in the same place and does not change (unless of course you defragment your hard drive). SRAM has many differences to Dynamic RAM (DRAM). for that matter. Static RAM is a type of RAM that gets its data without an external refresh.