Video: Richard Buckland: Inside a Computer (poor sound after 50 minutes as he knocks the microphone)
Components: CPU, bus, processor, memory, I/O ports (interfaces), system clock.
Includes:
ALU (Arithmetic-Logic Unit, where arithmetic and logical operations are carried out);
Registers (Accumulator, Program Counter, Index, Data, Address, Instruction, Status)
Types:
RAM - Random Access Memory (Read-Write). Programs and some immediate data stored here e.g. spreadsheet or word processor document (sections large documents may be 'paged' - kept on disc - database programs may load only a single record from disc, not whole file). Volatile.
ROM - Read Only Memory. store bootstrap loader to start copy of operating system from disc to memory when computer switched on. Non-volatile.
PROM - Programmable ROM. All ROM is PROM at some stage. Programmed locally for use in computer to store small programs permanently. e.g. for embedded devices
EPROM - Erasable PROM. Useful for recycling unwanted PROMs.
Cache - on processor so very fast, used for storing recently used instructions and data so no need to fetch all the way from memory.
Data bus: carries data between memory and processor and also between ports and other parts e.g. sound card, graphics card, have own processors and memory and some data are moved to processor and main memory; bi-directional, data flow to processor and back to memory.
Address bus: carries address from processor to location in main memory (some ports may be memory-mapped so have addresses too); unidirectional, no need for an address to flow back to processor.
Control bus: carries signals from processor to parts of CPU and system to activate something e.g. to read or write data to a memory location or I/O device.
Many of these. Need to know their characteristics, how they are used and why you might choose one rather than another.
Keyboard. Scanner. Mouse. Bar code scanner. Track ball. Graphics tablet. Magnetic stripe reader. Optical character reader. Touch-sensitive screen. Magnetic Ink character recognition (MICR). Speech synthesiser.
Printer. Microfilm.
Provides regular pulse to computer e.g. 100MHz
Program Counter (PC) to address bus - address of next instruction (Signal sent on control bus to read)
Processor reads data bus and instruction moves from memory to instruction register
Processor executes instruction and increments program counter
Magnetic Disk - has platters (magnetic disc), cylinders (one platter above another), sectors (like slices of cake) and tracks (circles, not spiral)
Floppy Disc - still has its uses, though these are fading. Mainly for transporting small files (better to use Internet? e.g. ftp).
Magnetic Tape - for system backup and storage of large datasets e.g. DVLC. Inter-Block Gap.
Optical Disc - e.g. CD. Data put on disc surface with laser. Early types were WORM (Write Once Read Many times). High storage capacity so used for distributing software. Slower and less capacity than hard disc and less capacity than tape. Persoanl back-up or archiving of e.g. photographs.
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