1. COMP 2130 Intro Computer Systems Thompson Rivers University
C Programming
Winter 2012
COMP 2130 Intro Computer Systems
Computing Science
Thompson Rivers University

2. Course Contents Part I – Review Part II – C Programming Language
Mumber Systems
Boolean Logic
Digital Logic
Part II – C Programming Language
Part III – Introduction to Computer Systems
Not the replacement of IPv6; Inter-transition mechanism; But if IPv6 would fail
TRU-COMP2130
C Programming

3. Unit Learning Objectives
Use a char array as a string.
Use printf() function to print messages.
Use pointers and references.
Use pointers for dynamic memory management.
Use open(), read(), write(), close(), and FILE* functions to manipulate files.
Use user-defined data structures.
Use bitwise operators.
...
TRU-COMP2130
C Programming

4. Unit Contents References Basic C
Basic C
Primitive Data Types, Operators, and printf()
...
TRU-COMP2130
C Programming

5. Why C? Why C? Pros and cons How is C different from Java?
Most system programs are written in C, not even C++, for fast execution.
The kernels of most operating systems are written in C.
Pros and cons
Fast execution \
Easy to handle memory - > Good for system programming
Bit operation /
But complex concepts of pointer, type conversion and memory allocation
How is C different from Java?
TRU-COMP2130
C Programming

6. How is C different from Java? C
Java
Procedural
No class
Common data: global variables
Abstract data type: struct, union
Object oriented
Class
Common data: instance variables
Abstract data type: class
Micro approach
Individual utility libraries
Macro approach
Utilities include language itself
Reference type variable
No reference, but objects include the concept
Call by value; call by reference
Call by value; call by reference for objects
Compiling
One file at a time, and linking
Cross-reference
TRU-COMP2130
C Programming

7. Basic C
# include <stdio.h> // import statements in Java
# include <stdlib.h>
# define PI // final instance variables in Java
// global variables // instance variables in Java
int level = 0;
// functions // methods in Java
void prt(char[] s) {
printf(“%s”, s);
printf(“This is a level-%d programming course.”, level); }
// main() // main method in Java
int main(int argc, char* argv[])
level = 2;
prt(“Welcome to C Programming\n”);
TRU-COMP2130
C Programming

8. Look at the programming style!
// program1-1.c
// Definitions including header files and functions
#include <stdio.h>
// Declarations of global variables
// Functions
int main() {
// Declarations of local variables
double radius, circumference; /* declare an input and output items */
// codes
radius = 2.0; /* set a value for the radius */
circumference = 2.0 * * radius; /* calculate the circumference */
printf("The circumference of the circle is %f\n", circumference); // What is printf(...)?
// What is %f?
// printf("...", ...);
// return statements
return 0; }
Look at the programming style!
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C Programming

9. How to compile? How to execute? How to find manuals?
$ gcc program1-1.c It will create a.out.
$ gcc –o prgm program1-1.c It will create prgm.
How to execute?
$ ./a.out
$ ./...
How to find manuals?
$ man –s 3 printf
$ man –s 3 scanf
$ man –s 3 rand
...
TRU-COMP2130
C Programming

10. Data Types, Operators and printf()
Primitive data types
char unsigned char byte in Java
short unsigned short short
char in Java uses 2Bs.
int unsigned int int
long unsigned long long
no unsigned in Java
float float
double double
// boolean? TRUE: any non-zero value, boolean in Java
FALSE: zero
// string? “...” String
sizeof(data_type) or sizeof(variable) gives the number of bytes used.
TRU-COMP2130
C Programming

11. Arithmetic operations
= assignment
+ addition
++ increment by one
- subtraction
-- decrement by one
* multiplication
/ division
% modulo
Boolean operations
&& AND not bitwise AND
|| OR not bitwise OR
Bitwise operations – will be discussed later
Reference operations – will be discussed later
TRU-COMP2130
C Programming

12. printf() formats in C System.out.print() in Java
printf(“...”, ...); // format, and variables
// the number of variables must be equal to the % formaters and
// must have the same data types
%s string, i.e., char[] having an element of ‘\0’ as the end specifier
%c character; char type
%d; %i integer; char, short, int, long type
%3d 3 places for the integer
%u integer (unsigned) – decimal; char, short, int, long type
%x; %X integer (unsigned) – hexadecimal; char, short, int, long type
%f float, double type
%5.2f 5 places for mantissa, 2 places for fraction
%e; %E exponential form; float, double type
\n, \t, \\, \”, %% newline, tab, \, ”, %
int t = 10;
printf(“Hi %c %d %s\n”, ‘a’, t, “there!”);
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C Programming

13. Examples program2-1.c program2-2.c program2-3.c program2-4.c
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C Programming

14. math.h Some MATH related functions # include <math.h>
double sqrt(double)
double pow(double, double)
double fabs(double)
Link with –lm -lm means libm.a, that contains
math utilities, is used
$ gcc program3-5.c –lm
Examples
program3-5.c
program3-6.c
TRU-COMP2130
C Programming

15. Reading User Inputs Some input functions that read data from keyboard
First, a reference operator and the related format specifier
&any_variable the addresss of the variable in the main memory
int addr = 10;
char c = ‘A’;
double x = 34.59;
printf(“%d, %p\n”, addr, &addr); // %p for address
printf(“%c, %p\n”, c, &c);
printf(“%f, %p\n”, x, &x);
printf(“%d, %d\n”, sizeof(addr), sizeof(&addr));
Examples
program2-13.c
TRU-COMP2130
C Programming

16. scanf(“...”, ...) “format”, address of a variable
int size; scanf(“%d”, &size); // why &size ???
char c; scanf(“%c”, &c); // why &c ???
Examples
program3-9.c
program3-10.c
program3-11.c
program3-12.c
program3-18.c
program3-19.c
char getchar(); get a character
char c = getchar();
program3-10.c // interesting example of character inputs
TRU-COMP2130
C Programming

17. Control Structures if How to use Boolean values or expressions?
if-else
if-else-if
switch-case
Examples
program4-1.c
program4-2.c
program4-3.c
program4-4.c
program4-5.c
program4-6.c switch-case
program4-7.c
program4-8.c
program4-9.c
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C Programming

18. for while do-while Examples program5-1.c ... program5-20.c
TRU-COMP2130
C Programming

19. Functions What is a function? Why do you need to use functions?
Pass by value
When a varible is passed to a function, the content of the variable is passed, not the variable itself.
Examples
program6-1.c function prototypes; call by value
program6-2.c scope
program6-3.c
program6-4.c return value from a function
how to return multiple values?
program6-5.c
program6-6.c use of multiple functions
program6-7.c
program6-8.c use of time() and random numbers
program6-9.c function prototypes as global variables
program6-10.c handling characters
program6-11.c handling strings – atoi(), atof()
TRU-COMP2130
C Programming

20. Scope Rules Global variables and local variables
Global variables declared outside any function are visible in all functions and shared.
Local variables declared inside a function (or a block using ‘{‘ and ‘}’) are visible only in the function.
Examples
program7-1.c local and global scope
program7-2.c how to keep a value in the next invocation?
program7-3.c static local variables
Is it a good idea?
Let’s make a function to swap two values.
Case 1: the swap function in the same file with main()
Case 2: the swap function in another file
$ gcc file_1.c file_2.c
TRU-COMP2130
C Programming

21. Pointers Pointers are not supported by Java Reference operations
A pointer type variable can hold the address of a varible of the same data type.
Declaration of pointer type variables
int* test;
char *string;
... // any data type
How to obtain the address of a variable?
... = &num;
TRU-COMP2130
C Programming

22. Examples TRU-COMP2130 int *test; int number = 20; test = &number;
printf(“%d, %d, %p, %p\n”, number, *test, test, &test);
// the content pointed by test
// the content of test
*test = 30; // into the memory pointed by test
printf(“Enter an integer: ”);
scanf(“%d”, &number); // the address of number
printf(“%d, %d, %d, %p, %p, %p\n”, number, *test, *(&number), test, &test, &number); // the content pointed by test
// the content pointed
// by the address of number
// the address of test
// the address of number
TRU-COMP2130
C Programming

23. Examples program7-4.c program7-5.c program7-11.c recursion
TRU-COMP2130
C Programming

24. Pass by reference Function prototypes Function declarations
void newval(float*);
Function declarations
void newval(float* xnum) { *xnum = 5; ... }
Example of function invocation
float* x; float y;
newval(x); newval(&y);
Examples
program7-6.c
program7-7.c
program7-8.c return of two values by using references
program7-10.c swap()
TRU-COMP2130
C Programming

25. Arrays Declaration and initialization Passing array variables
program8-2.c
program8-3.c
program8-7.c 2-D array
program8-8.c
Passing array variables
program8-4.c the size of an array is defined in function spec
program8-5.c the size of an array is passed as a parameter
program8-6.c
program8-9.c
program8-11.c liear search
program8-14.c bubble sorting; array passing as reference
program8-12.c binary search
TRU-COMP2130
C Programming

26. Array and reference Examples int number[10];
printf(“%p\n”, &(number[0]));
printf(“%p\n”, &(number[5]));
printf(“%p\n”, number); // related to reference
printf(“%p\n”, number + 5); // the address of number[5]
// not 5 * 4
newval(number);
void newval(int num[]) { num[0] = 5; ... }, or
void newval(int* num) { *num = 5; num[1] = 10; ... }
Examples
program8-1.c
program8-10.c
TRU-COMP2130
C Programming

27. Arrays and pointers are well related.
int number[10]; int *p, *q;
*p = 10; // Is it wrong?
p = number;
q = &number[0];
number[0] = 2; number[1] = 9; number[2] = 5;
printf(“%p, %p\n”, p, q);
printf(“%d, %d, %d, %d\n”, *(p+1), p[1], *(q+1), q[1]);
Examples
program11-2.c increment of a pointer value
program11-3.c array as a reference
program11-4.c increment of a pointer value;
array as a reference
program11-5.c
program11-7.c char*
program11-8.c array of pointers
program11-9.c
Arrays and pointers are well related.
TRU-COMP2130
C Programming

28. Do we really need to use pointers? Dynamic memory management
#include <stdlib.h>
void *malloc(int size); // allocate size bytes
// and return the addr
void free(void *); // free the memory space
Let’s make a dynamic queue.
TRU-COMP2130
C Programming

29. String sprintf(tmp, “course name is %s.”, name); TRU-COMP2130
char name[256], tmp[256];
name[0] = ‘C’;
name[1] = ‘O’;
name[2] = ‘M’;
name[3] = ‘P’;
name[4] = ‘\0’; // it is very important.
name[5] = ‘ ’;
name[6] = ‘2’;
name[7] = ‘1’;
name[8] = ‘3’;
name[9] = ‘0’;
name[10] = ‘\0’; // it is very important.
printf(“course number = %s\n”, name);
printf(“%p\n”, name);
printf(“course number = %s\n”, &(name[5]));
scanf(“%s”, name);
sprintf(tmp, “course name is %s.”, name);
TRU-COMP2130
C Programming

30. #include <string.h.> Examples
program9-1.c gets(), puts()
program9-2.c stringcopy()
program9-3.c getchar()
program9-4.c getline()
program9-5.c strcpy(), strlen(), strcmp(), strcat()
program9-6.c toupper()
program9-7.c
program9-8.c
program9-9.c
program9-10.c
program9-11.c
TRU-COMP2130
C Programming

31. Files Example: Let’s make a file copy program. TRU-COMP2130
#include <stdio.h>
FILE *in, *out;
in = fopen(“in_filename”, “r”); // mode: r, w, a, r+, w+, a+
if (in == NULL) ...
out = fopen(“out_filename”, “w”);
fclose(in);
fprintf(out, “format ...”, variables...);
fscanf(...);
fgets(...);
int fseek(FILE*, long, [SEEK_SET|SEEK_CURRENT|SEEK_END); move file position pointer
int fwrite(char*, int size, int nmemb, FILE*);
int fread(char*, int size, int nmemb, FILE*);
fputc(...);
fgetc(...);
Example: Let’s make a file copy program.
TRU-COMP2130
C Programming

32. Examples program10-1.c <stdlib.h>, exit(), FILE*, fopen(), NULL
program10-2.c fopen()
program10-3a.c
program10-3b.c
program10-4.c fprintf(), fclose()
program10-5.c fscanf(), EOF
program10-6.c fgets() // get a line from a FILE
program10-7.c fseek()
program10-8.c passing FILE*
program10-9.c returning FILE*
program10-10.c
program10-11.c
program10-12.c fwrite()
program10-13.c fread()
program10-14.c fputc(), fgetc()
TRU-COMP2130
C Programming

33. Structures User-defined data structure
struct struct_name { // class without methods in Java
data_type member1;
int num;
... };
struct struct_name test; // how to declare a struct variable
test.num = 10; // how to access a member
Examples
program12-1.c struct {...}
program12-2.c struct Date {...}
program12-3.c array of structs
program12-4.c passing a struct
program12-5.c struct pointer
program12-6.c malloc(), free()
Let’s make a dynamic queue.
TRU-COMP2130
C Programming

34. Bitwise Operations Examples | bitwise OR & bitwise AND ^ XOR ~ NOT
<< shift left
>> shift right
Examples
program14-1.c &
program14-2.c |, ^, ~, <<, >>
program14-3.c char* argv[], char**
program14-4.c
ipv4addr.c IPv4 address conversion
Assignments
Check if a target bit in an integer is 1.
Get the first three bytes in an integer.
TRU-COMP2130
C Programming