C Programming Revision

1. C Programming Revision Malcolm Wilson

2. Variables • Types int, char, double, long. NO type for string see later. • unsigned above. • assignment X=2 ; C=‘v’;

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

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

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

6. Boolean • Any value other than zero is true. • Watch out for == “is equal to”.

7. Control 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}

8. 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

9. 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);

10. 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) ;

11. Scope and storage class • Used for AVR • Static ,will remain even after function has exited. • Global • Volatile , can be changed by unpredicable actions.

12. Preprocessor directives • #include • “localfile” • <standard_locations> /usr/include • #define • #define WIDTH 80 • #define LENGTH ( WIDTH + 10 ) • #define u8  unsigned char

13. 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.

14. 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

15. 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;

16. 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.

17. 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’;

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

19. sizeof() • Used for malloc to allocate memory

20. Pointers and structures #include <stdio.h> #include <stdlib.h> main() { • printf("hello world \n"); • structmystruct{ • int age; • char buffer[20]; • }mydata; • mydata.age=45; • printf("age is %d \n", mydata.age); • structmystruct * d; • d=malloc(sizeof(structmystruct)); • d->age=53; • printf("pointed age is %d \n", d->age); }

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

22. 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}

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