What's a "high-level" computer language?

The next sections of the chapter present a C program to make a computer carry out, in effect, the same sequence of actions to calculate loan repayments. Note that essentially the same C program will work on practically any computer. This is a key advantage of using a so-called "high-level" language - it can be automatically translated or "compiled" into a form which can be executed on practically any computer. However, the precise procedures for entering the program, and arranging for it to be translated and executed will generally vary from computer to computer. For this reason, Alcock cannot and does not give detailed instructions for how to do this; however, you are given the appropriate detailed instructions, for the computers which you will be using, in the notes for Laboratory Session 2 .

Alcock next dissects this simple program in great detail, to explain, at least in a superficial sense, what its components are, and how they are interpreted by the computer. Ask yourself at this point if you can explain why a special language such as C is necessary at all - why can the computer not simply understand the original instructions written in English on p. 1?