This section is designed to tell you what RISC is and what an OS or Operating System is for. But first a quick bit of history.
We have seen in earlier sections that in the early days of computers when something the power of todays PC (personal computer) would occupy the whole of a large room a programmer would use a series of cards to program the machine. These cards were punched with a series of holes that formed a code or set of instructions. This code was in binary (ones and noughts). Every letter of the alphabet has a unique binary code to represent it so that a sequence can be built up which the computer then acts on. For example, suppose we were to tell a human to R.U.N. This sequence forms the instruction run which we would then interpret, the effect being that we would carry out the action. A computer works by translating an on/off sequence of electrical impulses. These can be represented in their simplest terms by a sequence of binary digits or BITs. In the very early computers a series of switches were used but this was laborious and rather slow so in came punched cards.
But to a human 1s and 0s are not very easy to understand. We have our own language made up of words which in turn are a selected sequence of letters of the alphabet. So it is easier for us to understand letters rather than numbers. So argued computer scientists and came up with a series of memonics to represent the intructions (eg ADD, AND). This was called assembly language, the basic 1s and 0s being machine code. However, this was still not very satisfactory. So throughout the 1960s a variety of languages more akin to English were developed. One of these is known as BASIC. Various dialects of BASIC emerged during the 1970s and early 1980s with a variety of commands to do different jobs. BASIC is known as a high level language. Machine code is a low level language.
However, after decoding the instructions they need to be actioned. The language program does all the decoding and turns the instructions into machine code but the actions that make up the instructions need to be controlled in some way. And then there are all the behind the scenes things that go on to support the language such as putting what you type in at the keyboard onto the screen or recording information on disk.
Now, most people know that at the heart of a computer is a microprocessor. This chip contains a set of instructions which can be represented by a set of memonics that differ from manufacturer to manufacturer and series to series. For example, the original BBC microcomputer used a chip called the 6502, whereas the ZX Spectrum used a Z80. There also existed a 6502C which carried out its instructions faster than the 6502 and also had a few additional instructions. One series of instructions will not work with another but you should be able to use programs written for one microprocessor with another in the same series.
Machine Control Windows Other Operating Systems
Contents Introduction Communications Input Numbers Systems Disks History