Computers can be classified based on the following criteria namely:
Generation/ origin.
Sizes.
Data types.
Purpose.
Classification based on generation/origin
A computer generation denotes the period of technology change in the development of computer system. These changes having grouped into first second third fourth fifth generations as discussed in the following paragraphs:
FIRST GENERATION COMPUTERS: 1945 to 1955
These are the computer built between 1945 and 1955. This generation of computers was made of thermonic valves and their designs based on the architectoinal design principle developed by john von neumann. They were big and bulky, applying much space. The equally generated so much heat and assault required much cooling. They were relatively difficult to program as it was programmed using a machine language. The storage device in the early computers were making delay line which we are based on sound transmission principles. Letter was the era of magnetic drums and tapes which way are followed by core storage. The core storage which is still in use as faster access time and not volatile. Difficulties also emanated in the input and output operation because of the use of mercury relay lines which was electromagnetic. This made it performance to be slower than the electronic central processing unit cpu and those causing the cpu to be almost ideal during the execution of input and output operation.
Examples of the first generation computers include:
EDSAC - electronic delay storage automatic computer.
EDVAC - electronic discrete variable automatic computer.
UNIVANC - universal accounting computer.
LEO -lyons electronic electronic office
ACE - automatic computer engine.
Second Generation Computers 1959-1964:
The second generation computers had their internal component made of transistors. Because of the advantages of the transistors as a switching element which includes being cheaper in manufacturing cost similar in size consuming less power and dissipating less heat lasting longer than the terminal valve higher reliability and faster processing time it overcame the demerit of vacuum tubes.
They were easier to program than the first generation computers and could be applied to a wider range of data processing jobs. There was a shift from machine language to easy use english high level language. Formula translation FORTRAN developed in 1957 was the earliest of such languages. Others like ALGON, APL,COBOL AND PASCAL were also used. Each high level language has features that may make it more suitable for a particular application than others and this dedicated the choice of language made by computer users. FORTRAN was particularly good for scientific computation while COBOL common business oriented language was tailored towards business data processing. Another remarkable development was made between 1959 and 1965 in the storage and input-output area with the introduction of high speed magnetic disk which enabled the random access of data and overcame tape related sequential access problems. Second generation of computers include IBM 7030, IBM 1401, LEO MARK III AND ATLAS whose use of magnetic disk storage recorded a great success that was sustained for a long time.
Third Generation Computers 1964-1970:
The technological innovation which ushered in this generation is the discovery of metallic oxide semiconductor is known as integrated circuits ics often called silicon chips. The silicon chips are made up of thousands of electrically connected transistors and other components package on one small chip. This computer's processed a greater input-output capabilities wilder internal storage and faster processing speed. This further development lead to low power consumption and dispersion less manufacturing cost requiring minimal cooling because of the use of ic . All these made them economical and attractive for use as mainframe and minicomputer. Examples of the third generation computers include ibm 360 icl 1900 series etc.
Fourth Generation Computers 1970-1982
These computers use tiny solid state device called microprocessors. The number of transistors that could be integrated on a silicon cheap increased every year. The scale of integration determines how many equivalent logic gate are put on one silicon chip which includes:
small scale integration ssi less than 12 logic gates .
Medium scale integration msi greater than 12 but less than 100 logic gates.
Large scale integration lsi greater than hundred logic gate and up to a few thousand.
Very large scale integration vls I that several thousands of equivalent logic gate are parked on one chip which can be held between the finger tips.
Super large scale integration s v l s i millions of equivalent logic gate can be contained in a single chip.
Again I see memory chips emerged as more viable male mercury element creating room for an increased storage capacity. This generation also witnessed the development of multiple programming and time-share which enable several users to make use of the same computer at a time and the same time such a way that it feels that he is using the computer alone. It's also witnessed the use of multi processes which share data processing task in one system. Example include intel 4004, intel 8080 , 8088,80286,80386 etc.
Fifty Generation Computers 1983-date.
The advancement in semiconductors continue to help in producing computers with smaller size, lesser cost, lower power consumption and dispersion, phoster capability, more reliability, increased efficiency and versatility .
One thing worthy of note is that microprocessors are still in use till date. New technologies like fibre optics quantum computing using component of chloroform molecule made up of chlorine and hydrogen atoms and magnetic resonance imaging mrt are being heard of now.
