StartingC

startingC: Learning the C Programming Language

Introduction

svn co http://source.ggy.bris.ac.uk/subversion-open/startingC/trunk ./startingC

A Quintessential First Program

OK, now that we have the example code, let's get cracking and run our first C program. First of all, move into the example directory:

cd startingC/examples/example1

We'll use of a Makefile for each example, so as to make the build process painless (hopefully!). All we need do is run make (see the [make tutorial about make] if you're interested in this further):

make

Now, we can run the classic program:

./hello.exe

and you should get the friendly response:

hello, world!

Bingo! We've just surmounted--in some ways--our hardest step; running our first C program. Given this quantum leap, everything else will be plain sailing from here, honest!

Types & Operations

Buoyed with confidence from our first example, let's march fearlessly onwards into the realm of variable types and basic operations. To do this, move up and over to the directory example2 and type make to build the example programs:

cd ../example2
make

Take a look inside types.c and after the start of the main function, you'll see a block of variable declarations:

  char   nucleotide;        /* A, C, G or T for our DNA */
  int    numPlanets;        /* eight in our solar system - poor old Pluto! */
  float  length;            /* e.g.  1.8288m, for a 6' snooker table */
  double accum;             /* an accumulator */

C, like many languages (e.g. Fortran), requires that variables must be declared to be of a certain type before they can be used, and here we see examples of four intrinsic types provided by the language. It's a very good habit to comment all your variable declarations, and here the comments pretty much explain what the various types are. double is a double precision--twice the storage space of a float--floating point number. The extra space make a double a good choice for an accumulator where you want to minimise rounding errors and avoid under- and overflow as best as possible. (The Fortran programmers amongst us will note, with a whince, the absence of an implicit type for complex numbers.)

int char float double

short & long

sizeof() casting

enumerated types

Now, it's very important that you muck around with these example programs as much as possible! Ideally, so much so that you break them! We never learn as much as when we make a mess of things, and since these are just toy programs, you may as well go for it! If you get in a pickle, you can get the original programs back with a quick waft of the Subversion wand:

svn revert *

Exercises

types.c

• do this
• then that

operations.c

• this
• that

Loops & Conditionals

if then else

(switch) case (default - fall through)

while and for

break & continue

Arrays & Pointers

address, dereference address arith 2d arrays binary trees and linked lists - just give examples

Structures

DAB again

watch out for padding

Further Reading

The bible is The C Programming Language by Kernighan & Ritchie.