(i) Cache Memory and Register
(ii) Bus topology and Star topology
(iii) Application software’s and system software’s
These are small and fast memories placed between the processors and main memory, though cache memory is very fast but being very expensive. It is used in small sized measurable in kilobytes such as 64 KB, 128 KB, 256 KB etc. These are used normally with PCs, which can have 32 to 128 MB of RAMs and even more. It works on the principle according to which it is said, whenever some locations is accessed then chances of accessing its nearly position in near future are high, Cache containing the copy of certain portions of main memory, whenever some memory read/ write operations is to be performed then first of all cache is checked for the desired data. If the desired data is present in cache then it is used directly by the CPU. If the desired is not present then a block of words is ready from main memory in to the cache. Cache is very small in size for the incoming block it is necessary that sufficient size slot if vacant in cache.
There is a movement of information between the various units of the computer systems. In order to handle this process satisfactory and to speed up the rate of information transfer the computer uses a number of special memory units called registers, These registers are used to hold information on a temporary basis and are part of the CPU (not main memory).
The length of a register equals the no. of bits it can store. Hence, a register that can store 8 bits is normally referred to as an 8 bit. Register. The size of the resisters sometimes called the word size. The bigger word size, the faster the computer can process a set of data.
A bus topology is shown in figure given below. All stations are connected to a single communication line. This single communication line is referred to as bus information frames originating at station are propagated away from the station in both directions on the bus. Each station on the bus interrogates the information frames destination address field for its own address, if the destination field does not match the station address, the station discards the information frame back on to the bus, if the destination address matches frame and process the frame.
A star topology is shown in figure below, in this topology a number of station as control communication on the connected directly to a central station or control station of a star topology can be bi-directional and are point to point. A station on this type of network passes an information frame to the central controlling which are forwars the information to the destination station. The central controller manages and controls all communications between stations are network.
Failure of a station on a star network is easy to detect and can be removed from the network. However failure of the central controller will disable communication through the whole network.
Application software is written to enable the computer to solve a specific data processing task. A number of powerful application software packages, which doesn’t require significant programming knowledge, have been developed, these are easy to learn and use as compared to the programming knowledge. Although these packages can perform many general and special functions, they are applications where these packages are not found adequate. In such cases, application programs is written to meet be written using important categories of software packages available are:
- Database Management software
- Spreadsheet software
- Word processing desktop publishing and presentation software, graphics software
- Data communication software
- Statistical and operational research software.
System software is generally supplied by the hardware manufacture. These are the software, which contribute to the control in performance of a computer system. The help in controlling the various functions of a computer like unloading of any software in main memory, storing new files, creating the files and so on. So these types of software are given a common name called system software. System software includes a variety of programs control monitors, assemblers’ translators, compilers, service and utility programs. All these software support and control the operation of any computer system.
Different categories of system software are:
(a) Operating systems and control programmers.
(b) Translator
(c) Applications Generator
(d) Utilities or service program.
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