Over view of computer system : Over view of computer system Computer Hardware : Computer Hardware Processor : Processor The processor is the part of the computer that actually does the computations. This is sometimes called an MPU (for main processor unit) or CPU (for central processing unit or central processor unit). Some computers have more than one processor. This is called multi-processing. The major kinds of digital processors are: CISC, RISC, DSP, and hybrid. : The major kinds of digital processors are: CISC, RISC, DSP, and hybrid. CISC stands for Complex Instruction Set Computer. Mainframe computers and minicomputers were CISC processors, with manufacturers competing to offer the most useful instruction sets. Many of the first two generations of microprocessors were also CISC. RISC : RISC It stands for Reduced Instruction Set Computer. RISC came about as a result of academic research that showed that a small well designed instruction set running compiled programs at high speed could perform more computing work than a CISC running the same programs (although very expensive hand optimized assembly language favored CISC). DSP : DSP stands for Digital Signal Processing. DSP is used primarily in dedicated devices, such as modems, digital cameras, graphics cards, and other specialty devices. Hybrid
processors combine elements of two or three of the major classes of processors. Main storage : Main storage Main storage is also called memory or internal memory (to distinguish from external memory, such as hard drives). RAM
Random Access Memory
the basic kind of internal memory. Slide 8: RAM is called “random access” because the processor or computer can access any location in memory (as contrasted with sequential access devices, which must be accessed in order) Slide 9: Most modern RAM is made from integrated circuits. At one time the most common kind of memory in mainframes was magnetic core, so many older programmers will refer to main memory as core memory even when the RAM is made from more modern technology. Static RAM : Static RAM It is called static because it will continue to hold and store information even when power is removed. Magnetic core and reed relays are examples of static memory. 2 kinds of RAM: Dynamic RAM : Dynamic RAM It is called dynamic because it loses all data when power is removed. Transistors and integrated circuits are examples of dynamic memory. It is possible to have battery back up for devices that are normally dynamic to turn them into static memory. ROM : ROM It is Read Only Memory (it is also random access, but only for reads).
It is typically used to store things that will never change for the life of the computer, such as low level portions of an operating system. EPROM : EPROM Erasable Programmable Read Only Memory, a special kind of ROM that can be erased and reprogrammed with specialized equipment (but not by the processor it is connected to). Slide 14: EPROM’s allow makers of industrial devices (and other similar equipment) to have the benefits of ROM, yet also allow for updating or upgrading the software without having to buy new ROM and throw out the old (the EPROMs are collected, erased and rewritten centrally, then placed back into the machines). external storage : external storage also called auxiliary storage
is any storage other than main memory. In modern times this is mostly hard drives and removable media (such as floppy disks, Zip disks, optical media, etc.). Slide 16: Sequential access devices (such as tape drives, paper tape punch/readers, or dumb terminals) provide for off-line storage of large amounts of information (or back ups of data) and are often called I/O devices (for input/output). Slide 17: Some devices are inherently input-only (also called read-only) or inherently output-only (also called write-only). Regardless of whether a device is I/O, read-only, or write-only, external devices can be classified as block or character devices. Character device : Character device A device that is one that inputs or outputs data in a stream of characters, bytes, or bits.
Character devices can further be classified as serial or parallel. Examples of character devices include printers, keyboards, and mice. Serial device : Serial device A device streams data as a series of bits, moving data one bit at a time. Examples of serial devices include printers and modems. Parallel device : Parallel device A device streams data in a small group of bits simultaneously. Usually the group is a single eight-bit byte (or possibly seven or nine bits, with the possibility of various control or parity bits included in the data stream). Slide 21: Each group usually corresponds to a single character of data. Rarely there will be a larger group of bits (word, long word, double word, etc.).
The most common parallel device is a printer (although most modern printers have both a serial and a parallel connection, allowing greater connection flexibility). Block device : Block device A device moves large blocks of data at once.
). Examples of random access block devices include hard disks, floppy disks, and drum drives. Examples of sequential access block devices include magnetic tape drives and high speed paper tape readers. Input : Input Input devices are devices that bring information into a computer.
Pure input devices include such things as punched card readers, paper tape readers, keyboards, mice, drawing tablets, touch pads, trackballs, and game controllers.
Devices that have an input component include magnetic tape drives, touch screens, and dumb terminals. Output : Output Output devices are devices that bring information out of a computer.
Pure output devices include such things as card punches, paper tape punches, LED displays (for light emitting diodes), monitors, printers, and pen plotters.
Devices that have an output component include magnetic tape drives, combination paper tape reader/punches, teletypes, and dumb terminals.