Lecture 1Understanding The Computer

Lecture 1Understanding The Computer - Computers CMPT 125...

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CMPT 125: Lecture 1: Understanding the Computer Tamara Smyth, [email protected] School of Computing Science, Simon Fraser University January 3, 2009 1 Computers A computer performs 2 basic functions: 1. executes a sequence of instructions ( program ) 2. stores and recalls information ( data ) We can characterize a computer by: its speed the type of instructions it can execute the capacity of its memory A computer system is made up of hardware and software . CMPT 125: Understanding the Computer, Lecture 1 2 Hardware The hardware refers to the electronic equipment that forms a computer system. These include: Central processing unit (CPU) : * responsible for executing programs Input/output (I/O) devices : * keyboard, mouse, monitor, controllers etc. Main memory * holds the program and data being processed by the CPU Secondary memory or “storage” devices : * hard disks, floppy disks, etc. CPU MAIN MEMORY INPUT/OUTPUT MEMORY EXTENAL USER Figure 1: A computer system. CMPT 125: Understanding the Computer, Lecture 1 3 The Central Processing Unit (CPU) The CPU reads and writes numerical values (instructions and/or data) to locations in the main memory. The CPU executes program instructions one at a time, and sequentially until directed otherwise. When we turn on our computer, the internal hardware gives the CPU the address of the first program instruction. CMPT 125: Understanding the Computer, Lecture 1 4
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The CPU components the control unit : coordinates the transfer of data and instructions between main memory and the registers in the CPU registers : provides small memory storage in the CPU, e.g.: 1. instruction register : holder for current instruction being executed 2. program counter : holder for address of next instruction 3. general register(s) : temporary storage for values as needed arithmetic/logic unit : performs calculations CMPT 125: Understanding the Computer, Lecture 1 5 Transmission of Data Data must be moved to and from these various memory locations, to and from the CPU. The electrical pathways within the computer that allow components to communicate with each other are called buses . Computer components (such as the CPU and the various types of memory), are laid out on a board, called the motherboard , with the buses connecting them together. All data, instructions and any other signals, travel on the bus. CMPT 125: Understanding the Computer, Lecture 1 6 System Clock A clock generates an electronic pulse at regular intervals which synchronizes the events of the CPU. The rate of the clock determines the clock-speed , and give an idea of how fast the CPU and process instructions (different processors may process a different number of instructions per clock cycle). CMPT 125: Understanding the Computer, Lecture 1 7 The Main Memory The main memory holds both programs and data.
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