1. The Elements of Programming Style

2. References The elements of programming style by Kernighan and Plauger
The practice of programming
by Kernighan and Pike
The pragmatic programmer
by Hunt and Thomas

3. What distinguishes journeyman from master?
Attitude
Style
Philosophy

4. Documentation The only reliable document is the code.
A comment is of <=0 value if it is wrong.
Make sure comments and code agree.
Don’t just echo the code with comments – make every comment count.
Don’t comment on bad code – rewrite it.
Comment functions and global data.
Don’t over-comment.

5. Names Use descriptive names for globals, short names for locals.
Be consistent.
Use active names for functions.
Be accurate.

6. Using descriptive names for globals and short names for locals.
int npending = 0;
for (theElementIndex=0; theElementIndex<numberOfElements; theElementIndex++)
elementArray[theElementIndex] = theElementIndex;
for (i =0; i<nElem; i++)
arr[i] = i;

7. Be consistent. class UserQueue { }
int noOfItemsInQ, frontOfTheQueue, queueCapacity;
… …. }
int nitems, front, capacity;

8. Use active names for functions
int getHour();
bool isEven(int n);

9. Be accurate
bool isOdd(int num) {
return (num%2 == 0); }

10. Expressions and statements
Say what you mean, simply and directly.
Use the natural form for expression.
Parenthesize to resolve ambiguity.
Break up complex expressions.
Replace repetitive expressions by calls to a common function.
Be careful with side effects.
Use the “telephone test” for readability.

11. Say what you mean, simply and directly.
int v[10][10];
for (int i = 1; i<=10; i++)
for (int j = 1; j<=10; j++)
v[i-1][j-1] = (i/j)*(j/i);

12. Use natural form for expression
if (!(block_id < actblks) || !(block_id >= unblocks))
if ((block_id >= actblks) || (block_id < unblocks))

13. Parenthesize to resolve ambiguity.
*this.hour
(*this).hour or *(this.hour)?

14. Break up complex expression
*x += (*xp = (2*k <(n-m)?c[k+1];d[k--]));
if (2*k < (n-m))
*xp = c[k+1];
else
*xp = d[k--];
*x += *xp;

15. Be careful with side effects
scanf(“%d %d”, &yr, &profit[yr]);
scanf(“%d”, &yr);
scanf(“%d”, &profit[yr]);

16. Consistency and idioms
Use a consistent indentation and brace style.
Use idioms for consistency.
Use else-if for multi-way decision.

17. Use idiom for consistency
while (i <= n-1)
array[i++] = 1.0;
for (i=0;i<n;)
for (i=n;--i>=0;)
array[i] = 1.0;
for (i=0;i<n;i++)

18. Use idiom for consistency
do {
c = getchar();
putchar(c);
} while (c!=EOF);
while ((c=getchar())!=EOF)

19. Use idiom for consistency
int i, *iArray, nmemb;
iArray = malloc(nmemb*sizeof(int));
for (i = 0; i<=nmemb; i++)
iArray[i]=i;
for (i = 0; i<nmemb; i++)

20. Use else-if for multi-way decisions
if (argc == 3)
if ((fin=fopen(argv[1],”r”)) !=NULL)
if ((fout = fopen(argv[2],”w”)) != NULL) {
while ((c = getc(fin)) !=EOF)
putc(c,fout);
fclose(fin);
fclose(fout);
} else
printf(“Can’t open output file %s\n”, argv[2]);
else
printf(“Can’t open input file %s\n”, argv[1]);
printf(“Usage: cp input file output file\n”);

21. Use else-if for multi-way decisions
if (argc != 3)
printf(“Usage: cp input file output file\n”);
else if ((fin=fopen(argv[1],”r”)) ==NULL)
printf(“Can’t open input file %s\n”, argv[1]);
else if ((fout = fopen(argv[2],”w”)) == NULL)
printf(“Can’t open output file %s\n”, argv[2]);
else {
while ((c = getc(fin)) !=EOF)
putc(c,fout);
fclose(fin);
fclose(fout); }

22. Avoid function macros while ((a=getchar() !=EOF) && isupper(a))
#define isupper(c) ((c)>=‘A’ && (c) <=‘Z’)
while (isupper(a = getchar()))
while ((a=getchar() !=EOF) && isupper(a))

23. Parenthesize the macro body and arguments
#define square(x) (x)+(x)
1/square(y)
will be expanded to
1/(y)+(y)
#define square(x) ((x)*(x))
1/((y)+(y))