what is the different between if-else and switch statment
(other than syntax)

Answer Posted / mikew

The switch branches on one value only, whereas the if-else
tests multiple logical expressions.

So you could say that the switch is a subset of if-else.

The potential difference if that switch is conceptually an
N-way branch point, whereas the if-else is always a
(repeated) binary branch.

However, if you are checking, say, a return code, against a
varied list of possibilities, then the switch can give
greater clarity to source code - and allow simpler addition
of new cases, making it easier for maintenance, as well as
allowing the compiler to generate simpler code.

Simpler code is possible because it can generate a jump
table to perform the multiple comparisons, i.e. in pseudo-code:

_jump_table:
DEFW case1_address
DEFW case1_value
...
DEFW caseN_address
DEFW caseN_value
DEFW NULL /* terminator */

- search _jump_table for case_value
- branch to corresponding case_address, or take default
action if NULL terminator found instead.

In the special case that case1 ... caseN values are
sequential numbers (maybe with a few gaps) then the table
and code can be further simplified as a simple indexed branch:

_jump_table:
DEFW case1_address
...
DEFW default_address /* fill in any holes !*/
...
DEFW caseN_address

- check value is between case1_value and caseN_value
- subtract case1_value
- load branch address word from _jump_table word-indexed on
previous result

Is This Answer Correct ?    27 Yes 14 No



Post New Answer       View All Answers


Please Help Members By Posting Answers For Below Questions

What is the basic structure of c?

779


What is a pointer variable in c language?

843


Why is c used in embedded systems?

852


How can I sort a linked list?

804


What is external variable in c?

815


What is time null in c?

767


Give basis knowledge of web designing ...

1779


What is fflush() function?

887


Write a function which takes as parameters one regular expression(only ? and * are the special characters) and a string and returns whether the string matched the regular expression.

862


Which is an example of a structural homology?

1046


Explain how do you determine the length of a string value that was stored in a variable?

915


what is the function of pragma directive in c?

883


Describe the difference between = and == symbols in c programming?

1017


Explain what standard functions are available to manipulate strings?

822


Write a program to print all permutations of a given string.

940