IT Groundwork ICS3UC - Unit 1 Hardware

Overview of Computer System

Input/Output Devices (I/O) Examples of input devices: – keyboard – scanner – microphone Examples of output devices: – monitor – printer – speakers

Memory Computer memory consists of blocks of bits called words. Word sizes vary from computer to computer. Each word will hold either data or program instructions. RAM Random Access Memory - temporary ROM Read Only Memory – permanent, cannot be changed

Storage Hard Drive Floppy Drives CD-ROM DVD R-CD-ROM RW-CD-ROM Zip Drives

The CPU contains a Control Unit, Arithmetic Logic Unit (ALU) and a small number of memory locations called Registers. Different registers perform different tasks such: as manipulating data, keeping track of the results of decision making operations, and pointing to the next instruction to be executed Central Processing Unit

Central Processing Unit Memory RAM ROM Input Devices Output Devices Secondary Storage Devices Computer Hardware Functions

Bits & Bytes Bit - Binary Digit; represented by a 1 or a 0 – abbreviated as b Byte - a fixed-size collection of bits – technically, minimum number of bits required to represent a character – generally, 8 bits – usually, the smallest addressable unit of storage – abbreviated as B

Computer Units Quantity/size/capacity – Kilo byte -- KB one KB is 1024 bytes (2 10 ) – Mega byte -- MB one MB is 1024KB = 1024x1024 bytes (2 20 ) e.g., 4096KB = 4MB – Giga byte -- GB one GB is 1024MB = 1024x1024x1024 bytes (2 30 ) – Tera byte -- TB one TB is 1024GB = 1024x1024x1024x1024 (2 40 )

Some Standard Contexts Memory = MB, megabytes Disk storage = Gigabytes CPU clock speeds = MHz (now GHz) Memory access times, = nanoseconds billionth CPU cycle time CPU switching times = picoseconds trillionth Disk access times = milliseconds