After you have written the program the next step is to save the program in a file with extension . c . This program is in high-level language. But this language is not understood by the computer. So, the next step is to convert the high-level language program (source code) to machine language (object code). This task is performed by a software or program known as a compiler. Every language has its own compiler that converts the source code to object code. The compiler will compile the program successfully if the program is syntactically correct; else the object code will not be produced.

The C Compiler

If you are working on UNIX platform, then if the name of the program file is testprog.c, to compile it, the simplest method is to type

cc testprog.c

This will compile testprog.c, and, if successful, will produce a executable file called a.out. If you want to give the executable file any other, you can type

cc testprog.c -o testprog

This will compile testprog.c, creating an executable file testprog.

If you are working with TurboC on DOS platform then the option for compilation is provided on the menu. If the program is syntactically correct then this will produce a file named as testprog.obj. If not, then the syntax errors will be displayed on the screen and the object file will not be produced. The errors need to be removed before compiling the program again. This process of removing the errors from the program is called as the debugging. 

Syntax and Semantic Errors

Every language has an associated grammar, and the program written in that language has to follow the rules of that grammar. For example in English a sentence such a “Shyam, is playing, with a ball”. This sentence is syntactically incorrect because commas should not come the way they are in the sentence.

Likewise, C also follows certain syntax rules. When a C program is compiled, the compiler will check that the program is syntactically correct. If there are any syntax errors in the program, those will be displayed on the screen with the corresponding line numbers.

Apart from syntax errors, another type of Basics of C errors that are shown while compilation are semantic errors. These errors are displayed as warnings. These errors are shown if a particular statement has no meaning. The program does compile with these errors, but it is always advised to correct them also, since they may create problems while execution. The example of such an error is that say you have declared a variable but have not used it, and then you get a warning “code has no effect”. These variables are unnecessarily occupying the memory.