What are the rules for determining legal identifiers in C language?

The rules are: 1. The first character of the identifier must be a letter (a~z or A~Z) or an underscore (_); 2. The following characters must be any letters, underscores (_ ), composed of numbers; 3. The uppercase and lowercase letters in the identifier are different and represent different meanings; 4. The identifier cannot be a keyword.

The rules for judging legal identifiers in c language are as follows:

(1) The first character must be a letter ( Case-insensitive) or underscore (_);

(2) followed by letters (case-insensitive), underscore (_) or numbers;

(3) in the identifier There is a difference between uppercase and lowercase letters. For example, the variables Sum, sUm, and suM represent three different variables;

(4) cannot have the same name as a special-purpose reserved identifier (ie, keyword) that has been predefined by the c compilation system. For example, identifiers cannot be named float, auto, break, case, this, try, for, while, int, char, short, unsigned, etc.

knowledge expansion

All keywords in C language:

auto

enum

restrict

unsigned

break

extern

return

void

case

float

short

volatile

char

for

signed

while

const

goto

sizeof

_Bool

continue

if

static

_Complex

default

inline

struct

_Imaginary

do

int

switch

double

long

typedef

else

register

union

Recommended tutorial: "C Language"

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