Chapter 4 - Chapter 4 Computer Architecture - how computers...

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Chapter 4 Computer Architecture - how computers work The computer itself is housed inside the system unit (the grey box on a desk). Most of the components of a computer are plug in circuit devices called microchips, chips, or integrated circuits. A chip is a piece of crystal with the equivalent of many wires, transistors, etc. burned into it. It is enclosed in black plastic and has many wires coming out of it which fit in sockets on a circuit board. The main circuit board is called the mother board. Some things found on a motherboard: RAM chips - temporarily store data being processed ROM chips - store the boot program, run system diagnostics (error checks), control low-level i/o. the CPU a bus transports data between components on the motherboard. Expansion slots - places that we plug in expansion cards for additional devices added to the computer. Expansion card - circuit board that contains circuitry to control a video display, a printer, a disk drive, modem, etc. port - a plug on an expansion card into which we plug a cable for the printer or telephone wire for a modem. Digital computers use binary codes to represent data. For numbers, they use the binary number system: 0 0 1 1 2 10 3 11 4 100 5 101 6 110 7 111 8 1000 9 1001 10 1010 11 1011 For characters, most computers use the ASCII code (Askey). Some IBM mainframes use EBCDIC. Letter A is 1000001 in ASCII and 11000001 in EBCDIC. 1000001 - 7 bits 11000001 - 8 bits value 64 + 1 = 65 128 + 64 x 1 = 193 Data transfer - uses a bus to move collections of data bits from one point to the other (just like a real bus moves multiple people at one time). A ribbon like cable with many individual wires. A bus runs from the CPU to memory and from memory to a disk drive. The address lines of a bus are used to carry the address (location) of each byte to be transferred. The data lines are used to carry the data bits.
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Usually 8, 16, or 32 bits are transferred at one time (a byte, a word, or double word). RAM - we've talked about it. A collection of storage locations arranged in groups of 8 bits (zeros or ones). Each location has its own address. The data in a particular address can be changed. RAM is volatile memory - all data in RAM disappears when the computer is turned off. RAM is important because it contains all the data for a program plus the program instructions themselves. RAM goes from 4 Megabyts to 32 Megabytes for todays PCs. The
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Chapter 4 - Chapter 4 Computer Architecture - how computers...

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