The document contains guidelines for coding in C including follow standards like ISO 9899, use approved escape sequences and data types, declare variables before using, use braces and indentation properly, avoid undefined behaviors like signed integer overflow, and restrict usage of certain functions and headers.

2.  1. ISO 9899 STANDARD
 2. COMBINATON OF C AND ASSEMBLY SHOULD
SUPPORT BY COMPILER
 4. RUN TIME CHECKING
 5. Use IOS C standard escape sequences
n, break, goto
 6. ISO 10646-1 rules for char types
 7. don’t use tri graphs
??-=~, ??)=]
 8. no multi byte char & wide string literals
Japanese, Chinese characters

3.  9. no nested comments
 10. not to comment code part
 11. Identifiers should not be >31
 14. char type should be signed or unsigned
 16. no bit representation of floating point
Use only decimal format
 17. typedef names shall not be reused
declare only once in header file

4.  18. use as bit_44 (suffix)
 19. octal constants shall not be used
c=052 052=42 in decimal
0 is used to represent for octal representation
 20. declarations of functions before using
 21. namespace shall not have same spellings
 24. no two identifiers should have internal &
external linkages
static i=0; extern i=0;

5.  25. An identifier with an external linkage
shall have exactly one external definition
 26. If objects are declared more than once
they shall have compatible declarations
delay function in multiple locations
 30. automatic variables have garbage values
 31. Braces shall be used to indicate and
match the structure in the non-zero
initialisation of arrays and structures

7.  Bit wise operations should not be
 Confused
 Performed on signed int
 38. shift operations
 16 bit integer should shift only in 0-15 range
 39. Unary minus
 t=100 and –t represents -100
 40. size of operator
 If(sizeof(y)==4) ok
 If(sizeof(f(z))==4) not ok
 41. Integer division based on compiler
 A=3/2
 A=3/-2
 A=3%2
 A/=2
 A%=-2
 42. comma operator should be used only in ctrl
expressions

8.  43. implicit conversions results in loss of
information
 Int32 I; int16 j,a;
 a=i*j;
 47. t=a*b+c/q; not ok
t=(a*b)+(c/q); ok
 48. int i=1,j=3; float k;
 K=i/j; to get precise value
 50. Float f=0.1234, g=0.1234;
 If(f==g) not to use

9.  52. every function should execute at least once
 54. if(i==k); while(1);
 Not to use
 Labels in switch statements
 Goto(avoid)
 Continue
 Break (use only in switch)
 If, if else, while must enclose in braces
 If, ifelse must have final else
 Every case of switch ends with break
 One default and one case is needed in switch
 Switch(x=y) don’t use
 Don’t use floating values for loop counters
 67.
 for(i=0;i<10;i++)
 {
 i=5;
 }

10.  Declare at file scope
 Variable no of arguments shall not be used
 Shall not call themselves
 Prototype declaration is needed
 Return type should match with the function
type
 Must have return type
 With no parameters declare as void

11.  #include---preceded by pre-processor directive
 C macros used
 #define pi 4
 Macros are not defined as #define’d
 Not to use #undef
 function-like macro shall not be 'called' without
all its arguments
 Arguments to a function-like macro shall not
contain tokens that look like pre-processing
directives
 each instance of a parameter, shall be enclosed
in parenthesis
#define TIMES2 ( x,y ) ( x* ( y ) )

12.  Identifiers in pre-processor directives should
be defined before use
 At least one preprocessor directive
 #pragma( libraries we can add to compilers)
need to be documented properly
 The defined pre-processor operator shall only
be used in one of the two standard forms
 #if defined d ok
 #if defined ( d ) ok
 #if defined "d" not ok

13.  Pointer arithmetic shall not be used
k = *pi;
k = * ( ++pi ) ; /* RULE 101 */
 No more than 2 levels of pointer indirection should be
used
k = ( *pi1 ) ;
k = ( * ( *pi2 ) ) ;
k = ( * ( * ( *pi3 ) ) ) ; /* RULE 102 */
 Relational operators shall not be applied to pointer types
except where both operands are of the same type
int m[10] = { 0,1,2,3,4,5,6,7,8,9 };
int n[10] = { 0,1,2,3,4,5,6,7,8,9 };
int *pm, *pmm;
pm = &m[1]; pmm = &m[3];
if ( pm < pmm ) { }
pmm = &n[3];
if( pm < pmm ) /* RULE 103 */ { }

14.  Non-constant pointers to functions shall not
be used
fp = ( int ( * ) ( ) ) func104b; /* RULE 104 */
 The null pointer shall not be dereferenced
 structure or union shall be fully specified
 struct s {
int mem;
foo; //108 rule
};
 Overlapping variable storage shall not be
used

15.  Bit fields shall only be defined to be one of
type unsigned int or signed int
static struct s{
int p_a : 4; /* RULE 111 */
signed int p_b : 4;
long p_e : 4; /* RULE 111 */} st;
 st.p_a = 0x1;
 Bit fields of type signed int shall be at least
2 bits long
 signed int p_a : 4;
 unsigned int p_b : 1;
 signed int p_c : 1; /* RULE 112 */
 All members shall be named and shall only
be access with their name
 unsigned int p_b : 1;
 signed int : 8; /* RULE 113 */
 unsigned int p_c : 4;

16.  Don’t change reserved key words
 Standard library names shall not be reused
 Should follow standard rules
 Dynamic heap memory allocation shall not be used
pd = malloc ( sizeof ( double ) ) ;
 The error indicator errno shall not be used
 Not to use
 Offsetof
 <local.h> and setlocale
 Setjmp macro, longjmp function
 Signal handling in <signal.h>
 <stdio.h>
 Atof, atoi, atol from<stslib.h>
 Abort, exit, getenv and system from <stdlib.h>
 Time handling of <time.h>