Programs in computer

In practical terms, a computer program might include anywhere from a dozen instructions to a lot of millions of instructions for something like a word processor or a web browser. A typical modern computer can carry out billions of instructions every second and nearly never make a mistake over years of operation.

Large computer programs may take groups of computer programmers years to write and the probability of the entire program having been written completely in the manner intended is unlikely. Errors in a computer programs are called bugs. Sometimes bugs are benign and it not affect the usefulness of the program, in some other cases they might cause the program to completely fail (crash), in yet other cases there may be subtle problems. Bugs are generally not the fault of the computer. Since computers merely execute the lot of instructions they are given, bugs are nearly always the result of programmer error or an oversight made in the program's design.