C basic grammar

C token (Tokens)

C program composed from a variety of tokens, the token can be keywords, identifiers, constants, string value, or a symbol. For example, the following C statement includes five tokens:

printf("Hello, World! \n");

This five tokens are:

printf
(
"Hello, World! \n"
)
;

semicolon;

In a C program, the semicolon is a statement terminator. That is, each statement must end with a semicolon. It indicates the end of a logical entity.

For example, here are two different statements:

printf("Hello, World! \n");
return 0;

Note

Notes like C program help text, they will be ignored by the compiler. They begin with / *, with the characters * / termination, as follows:

/* 我的第一个 C 程序 */

You can not nest comments within comments, which can not appear in a string or character values.

Identifiers

C identifier is used to identify the variables, functions, or the name of any other user-defined items. An identifier with the letters AZ or az or underscore _ Start, followed by zero or more letters, underscores and numbers (0-9).

Allowed punctuation characters, such as @, $, and% within C identifiers. C iscase-sensitive programming language.Thus, inC,Manpower andmanpowerare two different identifiers. Here are some valid identifiers:

mohd       zara    abc   move_name  a_123
myname50   _temp   j     a23b9      retVal

Keyword

The following table lists the C reserved words. These words can not be reserved as a constant name, variable name, or other identifier names.

C spaces

Line contains only spaces, known as a blank line, possibly with a comment, C compiler to ignore it completely.

In C, a space for describing the blanks, tabs, line breaks, and comments. Various parts of a space separate statements, so the compiler can identify the statement an element (such as int) where it ends, the next element where to start. Therefore, in the following statement:

int age;

Here, you must have at least one space character (usually a whitespace) between int and age, so the compiler to be able to distinguish between them. On the other hand, in the following statement:

fruit = apples + oranges;   // 获取水果的总数

fruit and =, = or space character between apples and is not required, but in order to enhance readability, you can add some appropriate spaces as needed.