Chapter 1 INTRODUCTION - William Paterson …

1 2017 Gilbert Ndjatou Page 1 Chapter 1 INTRODUCTION A digital computer system consists of hardware and software: The hardware consists of the physical components of the system. The software is the collection of programs that a computer can execute and a program is a sequence of step-by-step instructions that a computer executes in order to solve a problem or to perform a task. This Chapter discusses the concepts of a computer system hardware and software, computer programs, basic elements of a high-level language, structure of a high-level language program, functions, header files and the preprocessor, library functions, and the processing of a C/C++ language program. Computer System Hardware A computer system hardware consists of four major components: the Central Processing unit (CPU), the Main (or Primary) Memory, the input system, and the output system.

2 The general structure of a digital computer system hardware is shown in figure Main Memory The main memory (also called primary memory) is a collection of two-state devices. The states of each of these devices are used to represent binary digits or bits (0 or 1): one state represents 0 and the other represents 1. Consecutive bits in the main memory are grouped into units of 8 called bytes. A byte is characterized by two things: its address and its content. The address of a byte corresponds to its relative position in the main memory: the first byte is at address 0, the second at address 1, .. , etc. The content of a byte is the bit pattern that it represents. For example 0110 1001. The main memory holds the data to be processed by the computer and the program that it must execute in order to process it.

3 Central Processing unit The central processing unit (CPU) is the center of activities in a computer: it controls the operations of the other components of a computer, and also interprets and executes the instructions of a program. It consists of the control unit (CU), the Arithmetic and Logic unit (ALU) and the registers. The control unit (CU) controls the operations of the different components of a computer, and also interprets (or decodes) each instruction of a program. The Arithmetic and Logic unit (ALU) executes the instructions of a program. It can only perform the basic arithmetic operations of addition, subtraction, multiplication, and division, and logical operations 2017 Gilbert Ndjatou Page 2 such as comparing two numbers or the Boolean operations (AND, OR, or NOT).

4 Registers are high-speed memory locations within the CPU that are used to hold certain data. Figure General Structure of a Digital Computer System Hardware The arrows indicate the flow of data between the computer system hardware components. Input/Output Systems The Input system consists of the Input devices and their controllers. Examples of input devices are keyboards, microphones, scanners, and mice. An input device is used to transmit information from the outside world to the computer. The output system consists of the output devices and their controllers. Examples of output devices are printers, monitors, and speakers. An output device is used to transmit information from the computer to the outside world.

5 There is a controller between the CPU and each input/output device. For an output device, the controller accepts incoming data (as a sequence of bits) from the computer that it converts into the signals used by that device. CPUALUCUR egistersMainMemoryControllerInput DeviceOutput DeviceControllerControllerDriveSecondary Storage 2017 Gilbert Ndjatou Page 3 For an input device, the controller accepts signals from the device that it converts into sequences of bits to be used inside the computer. A device controller is also used for communication with the CPU: it accepts commands from the CPU and also lets the CPU know what is happening with the device. Secondary Storage A Secondary storage is used to permanently save data and programs for future use inside a computer.

6 Examples of secondary storages are flash drives, hard disks, tapes, CDs, and DVDs. A secondary storage can be used on a computer only if that computer has a drive that can read and/or write on that secondary storage. There is also a controller between the CPU and each drive: this controller converts signals from the secondary storage drive into bits that are sent to the main memory and vice versa. The collection of input devices, output devices, and the drives are referred to as system peripherals. System Interconnection The system interconnection consists of the wiring and the devices that allow data and control codes to move from one part of the computer system hardware to another. It is in general referred to as the system bus.

7 Exercise Part I Fill in the blanks with the most appropriate answers. 1. A _____ is a sequence of step-by-step instructions that a computer executes in order to solve a problem or to perform a task. 2. A digital computer system consists of _____ and _____. 3. The _____consists of the physical components of a digital computer system. 4. The _____ is the collection of programs that a computer can execute. 5. A _____ is a group of 8 consecutive bits. 6. The _____ of a byte corresponds to its relative position in the main memory. 7. The _____ of a byte is the bit pattern that it represents. 8. The _____ holds the data to be processed by the computer, and the program that it must execute in order to process it. 9. The _____ controls the operations of the different components of a computer system, and interprets and executes the instructions of a program.

8 10. The _____ controls the operations of the different components of a computer, and also interprets (or decodes) each instruction of a program. 11. The _____ executes the instructions of a program. 2017 Gilbert Ndjatou Page 4 12. _____ are special high-speed memory locations within the CPU that are used by programmers or the CPU to hold certain data. 13. The input system consists of the _____ and their _____. 14. The output system consists of the _____ and their _____. 15. An output device _____ accepts incoming data (as a sequence of bits) from the computer that it converts into the signals used by that device. 16. An input device _____ accepts signals from the device that it converts into sequences of bits to be used inside the computer.

9 17. A _____ is used to permanently save data and programs for future use inside the computer. 18. In order to use a particular secondary storage on a computer, that computer must be equipped with a _____ for that type of secondary storage and a _____ for the communication between the computer and the drive. 19. A computer system _____ is the collection of input devices, output devices, and the drives on that computer system. 20. The _____ consists of the wiring and the devices that allow data and control codes to move from one part of the computer system hardware to another. Part II. A. What are the four major components of a digital computer system hardware? B. What are the three major components of a CPU?

10 C. Provide three examples of each of the following components of a digital computer system hardware: a. input devices b. output devices c. secondary storage D. What are the major functions of each of the following components of a digital computer system hardware? a. main memory b. input device c. output device d. CPU e. secondary storage Computer Software A computer software is the collection of programs that it can execute. There are two major classes of computer software: system programs and application programs. An application program is a program that is executed by a computer in order to perform a specific task or to solve a particular problem for its user. Examples of application programs are word-processors, data base management systems, spreadsheet programs, and web browsers.