Which program to use with which punched cards.A JCL program would specify such things as: The program was written using a Job Control Language (JCL). An operator, therefore, needed to also write some instructions to do just that. Of course, if you were going to put lots of jobs together into a batch, and have lots of batches together, then there needed to be a way of managing and coordinating these different processes. It was possible to stack all of the input cards together for one batch process, and then also have some other input cards collected together for a different batch process. Similar jobs were collected together and put into a 'batch'. To improve the situation, a new input device was designed that could hold lots of punched cards. We have seen how buffers help overcome the problem of speed mismatch and we will meet this problem again later. This problem is sometimes referred to as a ' speed mismatch' problem.
If it has to wait while data is read into it or while data is sent out of it, then it won't be working to its full capacity. This changeover wasted a lot of the CPU's time. When the job had been finished, the next person could use the computer. The program would read the data, process it and then send the output to a printer. When both the program had been loaded up and the punched cards put into the input device, the program would be 'executed'. The input data might be held in a coded form on punched cards. If a person wanted to use a computer for something (a 'job') they would need to load their program into the computer and then load up the computer with the input data. In the early days of computers, operating systems were very basic.
One result of this is that there is now a wide range of types of operating system. They try to ensure that computer time is used as wisely as possible. Because of the high costs involved, computer designers and software designers spend a lot of time making sure that computers can do jobs efficiently. The equipment costs money and the infrastructure that ensures they are always working such as employing a network manager, for example, costs money.
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