What is Programming?

What will we cover?

An introduction to the terminology of computing plus some history and a brief look at the structure of a computer program.

Back to BASICs

Computer Programming is the art of making a computer do what you want it to do.

At the very simplest level it consists of issuing a sequence of commands to a computer to achieve an objective. In the Microsoft world MS DOS users used to create text files with lists of commands called BAT files. These simply executed the sequence of commands as a BATCH, hence the name. You can still produce these in Windows environments today but in practice they are rarely seen.

For example you might be producing a document (such as this tutorial) which comprises lots of separate files. Your world processor may produce backup copies of each file as it saves a new version. At the end of the day you may want to put the current version of the document (all the latest files) into a 'backup' directory/folder. Finally, to tidy up, delete all the backup files ready to start work the next day. A simple BAT file to do this would be:

COPY *.HTM BACKUP

DEL *.BAK

If the file were called SAVE.BAT then at the end of each day I could simply type SAVE at a DOS prompt and the files would be saved and backups deleted. This is a program.

Note: Users of Linux or other operating systems have their own versions of these files often known as shell scripts. Unix shell scripts are much more powerful than DOS BAT files, and support most of the programming techniques that we will be discussing in this course.

Let me say that again

If you were a little daunted by that, please don't be. A computer program is simply a set of instructions to tell a computer how to perform a particular task. It's rather like a recipe: a set of instructions to tell a cook how to make a particular dish. It describes the ingredients (the data) and the sequence of steps (the process) needed to convert the ingredients into the cake or whatever. Programs are very similar in concept.

A little history

Just as you speak to a friend in a language so you 'speak' to the computer in a language. The only language that the computer understands is called binary and there are several different dialects of it - which is why that cool iMac program won't run on your PC and vice versa. Binary is unfortunately very difficult for humans to read or write so we have to use an intermediate language and get it translated into binary for us. This is rather like watching Clinton and Yeltsin talking at a summit meeting - Clinton speaks, then an interpreter repeats what has been said in Russian. Yeltsin replies and the interpreter again repeats the sentence, this time in English.

Surprisingly enough the thing that translates our intermediate language into binary is also called an interpreter. And just as you usually need a different interpreter to translate English into Russian than you do to translate Arabic into Russian so you need a different computer interpreter to translate Python into binary from the one that translates BASIC into binary.

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