TABLE OF CONTENTS Computer software came into existence with the development of digital computers using stored programs, but there were precedents from prior machines. Analog computers previously used to solve engineering problems had to be programmed in terms of gain settings and patch panel configurations that could be characterized in an instruction set. Early electromechanical computers relied on a stack of punch cards initially developed to control textile machines. The earliest forms of computer programs were prepared in the detailed language of the machine, driven by the way the arithmetic unit and registers had to be controlled. The instructions were prepared as a sequence of words of a length corresponding to the size of the machine, written in the ones and zeros of binary arithmetic, indistinguishable from the ones and zeros of the data processed by the machine when not associated with their intended function.
Binary digital computers have come to be the principal means of accomplishing numerical and logical operations in machines because they can be made very reliable. This is accomplished by driving binary electrical circuits between the two states of cutoff and saturation, where one condition represents the number 1 and the other the number 0. If the machines employed base 10 arithmetic, they would forever be in maintenance while technicians...
