28 Programming and Data Structures
2.4 THEC KEYWORDS
The C keywords are reserved words by a compiler. All the C keywords have been assigned fixed
meaning. The keywords cannot be used as variable names because they have been assigned fixed jobs.
However, few C compilers allow to construct variable names, which exactly coincide with the keywords.
It is suggested not to mix up keywords with variable names. For utilizing the keywords in a program,
no header file is to be included. The descriptions of the keywords are explained in the different
programs/chapters. The C keywords are listed in Table 2.4.
Table 2.4 ‘C’ keywords
auto
double
int
struct
break
else
long
switch
case
enum
register typedef
char
extern
return
union
const
float short
unsigned
continue
for
signed
void
default
goto
sizeof
volatile
do
if
static
while
Additional keywords for Borland C
asm cdecl far huge interrupt near pascal
2.5 IDENTIFIERS
Identifiers are names of variables, functions, and arrays. They are user-defined names, consisting of
sequence of letters and digits, with the letter as the first character. Lower case letters are preferred.
However, the upper case letters are also permitted. The (_) under score symbol can be used as an
identifier. In general under score is used as a link between two words in long identifiers.
Example User defined identifiers are as follows:
a) #def ine N 10
b) #define a 15
Here, 'N' and 'a ' are user-defined identifiers.
2.6 CONSTANTS
The constants in C are applicable to the values, that do not change during the execution of a program. There
are several types of constants in C. They are classified into the following groups as given in Fig. 2.1.
Fig. 2.1 ‘C’ constants
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