DEVELOPMENT (PART II)
1948-1956
1948. The IBM 604 Electronic Calculating Punch Card machine became available. It could read punched cards, perform arithmetic operations, and punch the results on cards. The machine was programmed with a plugboard and was not a stored-program machine. It had over 1400 vacuum tubes to perform arithmetic operations using electronic registers.
1950. The SEAC (Standards Eastern Automatic Computer) was the first stored-program computer to be put into operation in the
United States. Built by the National Bureau of Standards in Washington, D. C., it used mercury delay lines for memory and was operational for more than a decade.
The ERA 1101, built by Engineering Research Associates of St. Paul, Minnesota, was the first computer to use a magnetic drum for main memory instead of mercury delay lines. It had 16,384 words of storage. Many different computers using magnetic drums for main memory were constructed during the period 1950-1955.
1951. The first UNIVAC (Universal Automatic Computer) was delivered. This machine was contracted by the National Bureau of Standards and delivered to the Census Bureau for use with the data of the 1950 census. It was designed by the Mauchly-Eckert team, used mercury delay lines for memory, and was the first commercially available stored-program electronic digital computer. A total of 48 of the UNIVAC-1 were built. Before UNIVAC-1 appeared, 60 other electronic computers had been built. No two were alike, and none of the programs developed for one were compatible with any of the others without major modification, or even redesign, of the computer.
Up to this point, computers were used almost exclusively for scientific purposes.
1953. The IBM 701 computer, a large-scale scientific computer using a Williams electrostatic memory tube backed up by a magnetic drum, was delivered. This machine had parallel binary arithmetic capability and was much faster than the UNTVAC for scientific computations.
1955. IBM introduced the IBM 702, the first large-scale computer designed for business purposes. The 702 weighed 24,600 pounds, contained approximately 5000 vacuum tubes, and required powerful air conditioning to cool the room where it operated. Actually, only a few of these computers were ever installed. As soon as IBM announced its newer, more powerful machine, the IBM 704, the 702 was withdrawn from the market—obsolete before it was even delivered.
1956. The IBM 704, first offered in 1956, achieved a nearmonopoly for IBM in the large-scale scientific computer field. It could handle 91 instructions, add in 24 microseconds, and perform either multiplication or division in 240 microseconds.
UNIT 3
THE SECOND GENERATION: 1957-1964
Second-generation computers featured early applications of concepts such as interleaving (the distinction of addresses among several independent memory modules) in direct addressing and effective addressing schemes. They had relatively large instruction sets, including these:
· Instructions for transferring information between the CPU and memory^ or between CPU registers
· Fixed-point as well as floating-point arithmetic instructions
· Logical (nonnumeric) instructions
· Instructions for modifying index registers
· Conditional and unconditional branching and related control instructions
· Input/output operations for transferring data between I/O devices and main memory
An important feature of second-generation machines was the provision of special branch instructions to facilitate the transfer of control between different programs, as in calling subroutines. I/O processors supervised the flow of information between main storage and I/O devices. They did so by executing special I/O programs, which were composed of I/O instructions and were stored in main memory.
Another important improvement of second-generation computers was batch processing. In first-generation systems, each user’s job was run separately, and the computer had to be halted and prepared manually for each new program. With the improvements in I/O equipment that came with second-generation computers, it became feasible to prepare a batch of jobs in advance, store them on a magnetic tape, and then have the computer process them in one continuous sequence, placing all the results on another magnetic tape. This mode of operation is termed batch processing. A small auxiliary computer was used to process the input and output magnetic tapes offline.
Second-generation systems also provided parallel processing techniques in two forms:
1. Overlapping the fetching and execution of instructions within a single program
2. Overlapping the execution of different programs—a single CPU system capable of concurrent execution of more than one program (multiprogramming)
