1. C Basics

2. Historical Background
Created at Bell Labs – to program Unix
Professional programmer's language
“stays out of programmer's way”
Assumption that programmers know what they want to do & how to use language constructs to accomplish it
Terse syntax
Small language – designed for efficiency
Type system & error checking – compile time only
Run time is very small (efficiency)
Programmer must handle memory management

3. Development Environment
Compiler – gcc
Open source compiler
OS – unix
Need to be able to work at command line
IDE
Eclipse
Codeblocks
Any editor (vi, emacs, …..)

4. Integer Types Integer char – 1 byte
short – small integer – at least 16 bits
int – default integer – at least 16 bits – hardware implementation
long – large integer – at least 32 bits
Portability problems
Can use typedefs to help

5. Integer Types char constants '\n' – newline '\t' – tab
'\0' – null character
'\O12' – character with octal value 12
int constants
0x10 – integer with hex value 10
O12 – integer with octal value 12

6. Integer Types Automatic “promotion” of integer types 'j' + 4
No overflow checking

7. Floating Point Types float – single precision floating point number
double – double precision floating point number
long double – possibly even bigger floating point number
Constants – default is double
3.14f
3.14l
Do not use equality (==) to compare 2 floating point numbers – round off error

8. C Syntax Comments – same as Java Variable declarations – same as Java
Case sensitive
Assignment operator – same as Java
Truncation – opposite of promotion – allowed in C
int n = 1000;
char c = n;
Value of c is whatever is in the bottom 8 bits of n
double pi = 3.14;
int n = pi;
n has value 3
No boolean – use int

9. Mathematical Operators
Same as Java
Logical operators
0 is false
Anything else is true
Bitwise operators
~ bitwise negation
& bitwise and
| bitwise or
^ bitwise exclusive or
>> right shift
<< left shift

10. Control Structures
Same as Java

11. Complex Data Types Arrays & records (structs) struct fraction {
int numerator;
int denominator; };
fraction f;
f.numerator = 2;
f.denominator = 5;
Arrays – similar to Java
No index checking
Constant pointer

12. Complex Data Types
Array of structs
struct fraction numbers [100];

13. Pointers * used to indicate a pointer int* n; char* c
struct fraction* f;
* to left dereferences pointer
*n – integer being pointed to by n (pointee)
(*f).numerator or f -> numerator
Example
struct fraction** f;
(*f) -> numerator
int* foo[20]

14. Pointers & Operator Returns address of (pointer to)
&n – address of n (pointer to n)
NULL
Symbolic name for 0 – pointer has no pointee
Pitfalls
Pointer must be declared & allocated
Pointee must be declared & allocated
Pointer must point to pointee

15. C Strings Array of characters – null character terminated
string.h library – support for strings defined in this way
Developer must manage the string memory & the null character terminator
Buffer overflow potential
strcpy does not check for size – just copies the characters
Better approach is to create the strings dynamically when size is known

16. C Strings
char*
Pointer to char – pointer to array of characters – string

17. Typedef Way of giving a name to a type
typedef <type> <name>
Examples:
typedef NULL UGA
typedef struct fraction frac
typedef struct treenode* tree
struct treenode {
int data;
tree left, right; }

18. Functions Syntax – same as Java All parameters – passed by value
Pass by reference – semantics can be achieved by passing pointer of argument
void swap (int* a, int* b) {
int temp = *a;
*a = *b;
*b = temp; }
int n = 2;
int m = 3;
swap (&n, &m);

19. Functions const Qualifier indicating that code cannot change variable
Ex:
void foo (const struct fraction* f);
foo cannot change fraction pointed by f

20. C Programs Main function int main()
Return value 0 – program terminates normally
Other values – error codes
Can have arguments for command line arguments
Prototype
Name & arguments for function
Must appear before implementation of function

21. C Programs Preprocessor – executes before compiler Directives
#define – establishes symbolic names
#include – copies text from another file
#if
If else logic used on symbols created by #define
Used at compile time to determine which code to compile
#once – prevents problems which can occur if a file is included more than once

22. C Programs Header files & source files Header files .h extension
contain prototypes
Source files
.c or .cc extension
contain implementations
assert
Macro implementation of assertions