C and C based languages - Conditionals and Loops

C and C based languages module C203

Conditionals and Loops

Exercises, examples and other material relating to training module C203. This topic is presented on public courses Learning to Program in C, Learning to program in C++, Programming in C, C and C++ Programming

Background

In this module, we study conditional statements like if and else that you use in C to have parts of your code run only if certain conditions are true, and loops such as while and for while provide the facilities through which you get parts of your code to repeat a number of times, or until a certain condition is met.

Articles and tips on this subject		updated
3397	Does a for loop evaluate its end condition once, or on every iteration? All the languages that we teach have a for loop or the equivalent, which is a clean way of repeating a block of code with a rising or falling index number. It's used in many circumstances - for example in iterating through the months of the year (for m goes from 1 to 12) of in stepping through all ...	2012-04-15
3384	Loops - a comparison of goto, while and for Almost every program you write, in any language, will have repeating code in it in the form of a loop. Programs without loops are limited to really simple "read a piece of data, calculate on it and print a result" tasks, and ever with them there will be loops within the function calls that you make ...	2011-08-10
3243	Breaking the running sequence - an introduction to conditional statements and loops A program is a series of instructions which are run in sequestially - or so you'll be told when you start programming. And, indeed, that's the default - the way it is unless you write code to do something different. "A program is a series of statemnets each separated by [something] which run one after ...	2011-04-11
3200	How a for loop works Java, Perl and other languages Java, Perl, PHP, Ruby, C, C++, Tcl and many other languages support a "for" loop construct. When your program enters the top of the loop, it performs the first statement in the brackets ... in this Perl example, that's to initialise the $now variable to 1. It then evaluates the expression given as ...	2011-03-18
962	Breaking a loop - Ruby and other languages When you're in a loop there are occasions you want to say get me our of this loop NOW, or "I'm done with the current iteration. And those are the 'classic' break and continue statements from C, C++ and Java. Languages like Perl changed break to last and continue to next ... and added a redo that asks ...	2011-01-29
3121	New year, new C Course Well - not completely a new course. New delegates, and lots of new examples written for them during the first day to that they can see not only WHAT work but also HOW the design of what works is put together during the day. Click on the individual source code examples, and you'll find programs to ...	2011-01-08
3004	Increment operators for counting - Perl, PHP, C and others Look at this Perl statement: $counter = $counter + 1; "Take the value in $counter, add 1 to it, and put it back in $counter". It's a common programing requirement - indeed, so common that you can write it in a shorter form in many languages: $counter += 1; "Add one to the value ...	2010-10-20
2570	Function Prototypes in C Programs other than the shortest are name up of named blocks of code (functions) into which parameters are passed and from which results are returned. And rather than have all the functions that make up an application in one file of source, you'll share them between several. That way, maintainable ...	2010-01-13
2002	New C Examples - pointers, realloc, structs and more Every time I program in C, I marvel at how clever the language is ... yet at the same time I curse some of the devices that are used to perform certain actions, which make the code that much more of a 'puzzle' to right. I've finished a 2 day C Programming course today ... and written a whole raft ...	2009-01-20
1696	Saying NOT in Perl, PHP, Python, Lua ... "Isn't there one standard way to say NOT?" asked one of my delegates on today's course - and it's an excellent question. But the answer to a question about a negative subject is itself in the negative - no, there isn't just a single way! In fact .. I can think of no fewer that 12 ways! • 1. ! ...	2008-07-05
1582	Ruby, C, Java and more - getting out of loops break and continue statements have been available for loop control for many years, and others functionallity has been added such as Perl's redo. From today's Ruby Course, here's a table that compares these loop controls in Ruby to similar commands in the other languages that I have been discussing ...	2008-03-19
1220	for loop - how it works (Perl, PHP, Java, C, etc) When writing a program, you'll often want to repeat a block of code, counting up through a table or performing a block of code with an input value (loop counter) that goes up 1, 2, 3, 4 etc. You COULD do this using a while loop, but this means you have to specify each of • how to start (initialise) ...	2007-06-07
1191	Smart English Output - via PHP and Perl ? : operator It's smart to have your program say "there IS in stock" or "there ARE 2 in stock" ... but if you write your code using an "if" and "else" type structure it can become quite verbose. The ? ... : operator - available in many languages including C, Perl and PHP - allows you to write a single "if,else" ...	2007-05-18
353	Wimbledon Neck What use is the "+=" operator? Why did the language designers bother to provide it? Yet they did ... In Perl and PHP $number_on_bus = $number_on_bus + $goton_here; becomes $number_on_bus += $goton_here; In Python number_on_bus = number_on_bus + goton_here becomes number_on_bus += goton_here In ...	2006-06-05

23b1

Examples from our training material

cb.c	Using { and } to scope a block
demo.h	Function prototypes for err.c and otherbits.c demo
eer.c	Program that makes use of ANSI C function prototypes
eight.c	loop showing weight loss needed until user is healthy
ex_203.c	Exercise - throw a die until you get a 6
fresh.c	looping via a goto
freshmeat.c	while loop - compared to goto loop and for loop
freshveggies.c	for loop - compare to goto loop and while loop
lp1.c	repeating code in a while loop
lp2.c	for loop - bad and good examples
makefile	makefile for module C203
otherbits.c	Functions used in function prototype demo (ANSI C)
seven.c	Conditional statements in C and C++
sindol.c	Singapore Teapot answer
sindy.c	Singapore teapot in C
tall.c	Temperature conversions using if
tall2.c	Temperature conversions using switch
tall3.c	Temperature conversions in a while loop
tall4.c	Temperature conversions with ++ and +=
tall6.c	Temperature conversions in a while loop
third.c	Conditional - if and else - example

Background information

Some modules are available for download as a sample of our material or under an Open Training Notes License for free download from http://www.training-notes.co.uk.

Topics covered in this module

The if statement.
Writing conditions in C.
Exercise.
if, else, elseif.
switch, case, default.
while.
++ and += operator families.
Exercise.
do while.
for.
break and continue.
goto and labels.
Layout of your blocks, and comments revisited.
Exercise.

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