C Programming Revision Malcolm Wilson

Variables

• • • Types int, char, double, long. NO type for string see later. unsigned above.

assignment X=2 ; C=‘v’;

Keywords

• C has a small number of “keywords” • http://tigcc.ticalc.org/doc/keywords.html

Standard I/O

• printf() • scanf() • Format specifiers %d, %f, %c, %s http://en.wikipedia.org/wiki/Printf http://en.wikipedia.org/wiki/Scanf

Operations

• • • +, -, *, /, %, ^ Operation dependent on variable type Try some

Boolean

• • Any value other than zero is true.

Watch out for == “is equal to”.

for(i=0, i<9, i++) { code block} while (x<8) {code block} if (y==2) {code block} elseif(y==7) {code block} else {code block}

Control

Control

switch( myvar) case 1 : {code block break;} case 2: {code block break;} default {code block} http://msdn.microsoft.com/en us/library/66k51h7a%28VS.80%29.aspx

Control

Code block is surrounded by {} if more than one line. Don’t need {} if code one line long.

eg for(i=0; i<5; i++) printf(“ number is: %d /n”, i);

Functions and Prototypes

• • • C is composed of functions, and must have at least one function called main().

Functions accept parameters and return values A “prototype” should be written which indicates what data types a function should accept and return.

– Eg int mynumberfunction( int num1, int num2) ;

Scope and storage class

• • • • Used for AVR Static ,will remain even after function has exited.

Global Volatile , can be changed by unpredicable actions.

Preprocessor directives

• • #include – “localfile” – /usr/include #define – #define WIDTH 80 – #define LENGTH ( WIDTH + 10 ) – #define u8 unsigned char

Arrays and strings

• • • • • int myarray[5]; int myarray[5]={1, 2, 3}; int myarray[]={1,2,3,4,5}; char mychararray=“malcolm”; A string is a “null terminated” char array.

Structures

struct struct_name { structure_member; ...

} instance_1,instance_2 instance_n; OR struct struct_name instance_1,instance_2 ,instance3 After defining the structure.

http://cprogramminglanguage.net/c-structure.aspx

Structures

• • Using typedef to avoid struct structurename all the time.

typedef struct{ unsigned int house_number; char street_name[50]; int zip_code; char country[50]; } address; address billing_addr; address shipping_addr;

Pointers

• • • • • Declared as using * int *p says p in a pointer to an integer.

p points to the memory location where a integer is stored.

Confusing , in the code. *p means the contents of memory location p.

And &p is the memory address of p.

Pointers and arrays

• • • myarray is the same as &myarray[0] So if an array is initialised as char name[]=“malcolm”; *(name+3) will be ‘c’;

Dynamic memory allocation

• • • • Allocates memory on the “heap” malloc(n) calloc(s, nbytes) intialises memory free();

sizeof()

• Used for malloc to allocate memory

Pointers and structures

#include #include } • • • • • { • • • • • • main() printf("hello world \n"); struct mystruct{ int age; char buffer[20]; }mydata; mydata.age=45; printf("age is %d \n", mydata.age); struct mystruct * d; d=malloc(sizeof(struct mystruct)); d->age=53; printf("pointed age is %d \n", d->age);

argv and argc

• int main (int argc, char *argv[]) { } • • argc , argument count argv , argument vector

Boo Boo’s in C

• • • Forgetting the semicolon Using = in a boolean expression instead of ==.

Completing a loop with no code being executed.

– while(test); { code block}

Deep C

• • • • Lvalues, Rvalues Inline functions Pointers to functions Pointers to pointers and multidimensional arrays.