Compiler

A compiler is a computer program that translates computer code written in one programming language into another programming language. The first language is called the source language, and the code is called source code. The second language is called the target and can usually be understood by computers. In that case, the instructions become machine code.

If a compiler can convert the same instruction text into machine code for different computers (like smartphones or video game machines), it is a 'cross-compiler'. If the compiler can make instruction text that is easier for people to read, it is a 'de-compiler'. People who write these instructions are called programmers. Some even made programs that can translate the instructions that describe how a compiler should work, into a compiler. That kind of program is called a compiler-compiler.

A compiler usually has three steps. It reads the text and makes notes about how the instructions go together. If the instructions don't make sense, it will try to tell the programmer. Then it will use what it knows about the target language to make the instructions fit better. It then writes down the instructions in the target language. If the source instructions are on different pages, it may have to compile several before it can write everything down.