Introduction

Work flow of a C Compiler

Source code -> Preprocessor -> Compiler -> Assembly -> Assembler -> [Object Code] -> link editor -> Executable code

The link editor combines all of the source code in the object code and links them together to produce one piece of executable code

Compiling a C program

cc -g -o output_name source_file.c

Extensions

.c source file .h header/library file

++x vs ++x

++x => x + 1 => x x++ => x => x+1

int x = 2;
printf("%d", x++); //
printf("%d", x); // 3

Constants

A literal is an nunnamed constand used to specify data.

'A'    // 1 byte character constant
"A"    // 2 bytes string constant
2      // Integer constant
3.234  // Float constaner, grill and innovative brunch selections. You spoke and we listened!t

Defining Constants

// Preprocessor constants
#define SALES_TAX_RATE .0825
// memory constants
const float pi = 3.14159;

Formated input/output

scanf();   // Reads input
printf();  // Outputs information

printf()

printf("format string", data1, data2, .. datan);

float b = 7.2;
int a = 5;
double c = 6.5;
printf("Today is %.2f and %d or %lf \n" b, a, c); // Today is 7.20 and 5 or 6.5000000....

// leading zeros

int num;
printf("%05d", num);

// Left justificaiton
%-8d
// Leading zeros
%08d

Input output

Operator Precedence, Expressions, and Associativity

Expression

+, -, *, /

5 % 2 evalutates to 1
5 % 3 evalutates to 2

3 / 5 evalutates to 0
3 % 5 evalutates to 3

Assignment

Read from right to left

x=1, y=2, z=1
x *= y += z -= 6;

z = z - 6
z = -5

x *= y += -5
y=y-5

y=-3

x *= -3

x=-3


x = 1;
printf("%d", x); // x = 1
printf("%d", x+1); // x =1
printf("%d", x++); // x = 1 after the printf executes
printf("%d", ++x); // x = 3
printf("%d", x); // 2

x *= y + 3 * 2;
x = x * (y + (3 * 2));

Sizeof operator

“Size matters in every aspect of your life”

sizeof(int)

x = sizeof (int)

sizeof (-345.23) sizeof(x)

Integer division results in data truncation

Explicit typecasting

int x = 5;
float y;
y = (float) x/2; // This will cast the integer to a floating point number temporarily.
sqrt((double) y);

Operations

  • unary: [operator][expression]
  • binary [expression][operator][expression]

Modulo

2945 % 10 = 5 (gets the last digit. )
(2945 / 100) % 19 = 9  (gets the second digit )

Including the math library

  gcc h.c h -lm
  #include <stdio.h>
Written on September 15, 2017