C Tutorial: Part 1. Dr. Charalampos C. Tsimenidis. Newcastle University School of Electrical and Electronic Engineering.

Transcription

1 C Tutorial: Part 1 Dr. Charalampos C. Tsimenidis Newcastle University School of Electrical and Electronic Engineering September 2013

2 Why C? Small (32 keywords) Stable Existing code base Fast Low-level

3 Terminology Source code: *.c type of files contain algorithms we are writing Header files: *.h type of files interface to libraries (possibly closed source) Library: Collection of functions for specific tasks Compiler: translates source code to an executable IDE: Integrated Development Environment provides comprehensive facilities to simplify code writing, compiling, debugging, etc.

4 First Example (Using Microsoft C++) Example: ex_p1_1.c 1 main() 2 { 3 4 } 1 Create a directory H:\C_Tutorial 2 Inside this directory, create a file ex01.c using notepad++ 3 Type the code segment above 4 Start Visual C++ Express command prompt 5 Change to the directory containing ex01.c using: cd H:\C_tutorial and H: 6 Compile using: cl ex01.c 7 Run program by double-clicking 8 Don t expect much as it does nothing!

5 First Example (Using Cygwin) Example: ex_p1_1.c 1 main() 2 { 3 4 } 1 Create a directory H:\C_Tutorial 2 Inside this directory, create a file ex01.c using notepad++ 3 Type the code segment above 4 Start the Cygwin shell 5 Change to the directory H:\C_Tutorial using: cd /cygdrive/h/c_tutorial 6 Compile using: gcc ex01.c -o ex01.exe 7 Run program by double-clicking or by typing./ex01.exe 8 Don t expect much as it does nothing!

6 Second Example Example: ex_p1_2.c 1 #include <stdio.h> 2 main() 3 { 4 printf("hello World!\n") ; 5 } Type the above code segment in a file ex02.c Compile and run the resulting executable Prints Hello World!

7 Third Example Example: ex_p1_3.c 1 #include <stdio.h> 2 3 int main(void) 4 { 5 //Print something 6 printf("hello World!\n"); 7 8 //Require keyboard input 9 printf("[press any key to continue]\n"); 10 getchar(); //Exit to operating system 13 return 0; 14 }

8 Standard C Library Total of 24 libraries: (< > indicates system library) A few commonly used libraries: #include <math.h> #include <complex.h> #include <stdio.h> #include <stdlib.h> #include <time.h> #include <string.h> For custom libraries: Library is in current folder: #include "csp.h" Library is in specific folder (Win): #include "H:\C_Tutorial\csp.h" Library is in specific folder (Linux): #include "/home/ct/c_tutorial/csp.h"

9 Comments Single-line comments: //... Multi-line comments: /*... */ Example: ex_p1_4.c 1 #include<stdio.h> 2 /* 3 This program prints hello world but also demonstrates 4 the use of comments to add code explanations 5 */ 6 int main(void) 7 { 8 // printf is included in stdio.h 9 printf("hello World!\n"); //Require keyboard input 12 printf("[press any key to continue]\n"); 13 getchar(); return 0; 16 }

10 Variable Types Specifiers 1 char 2 int 3 float 4 double 5 void Modifiers 6 short 7 long 8 signed 9 unsigned Qualifiers 10 const 11 volatile

11 Integer and Decimal Data Types Memory Range Data Type 8 bit unsigned char 16 bit unsigned int 32 bit unsigned long 8 bit signed char, char 16 bit signed int, int 32 bit long, long int Memory Range Data Type 32 bit 1.17E E+38 float 64 bit 2.22E E+308 double

12 Variables and Constants All variables and constants should be declared before utilisation: ex_p1_5.c 1 //Global variables 2 #define N 64 //integer constant 3 #define PI //floating point constant 4 const float pi= ; 5 #define SCALE (float)1/32768 //derived constant 6 float sample; //single floating point variable 7 double x=0.0; //double precision float variable 8 int n; //singed integer variable 9 unsigned count=0; //unsigned int variable initialised to void main(void) //main program start 12 { 13 //Local variables 14 int k, m; }

13 Flow Control: if, else, return, switch, case, default if syntax: 1 int m=0, n=0; if (n>10) 4 n=0; 5 6 if (n<10) 7 { 8 n++; 9 m--; 10 }

14 Flow Control: if, else, switch, case, default, break if-else syntax: 1 int m=0, n=0; if (n>10) 4 { 5 n=0; 6 m=0; 7 } 8 else 9 { 10 n++; 11 m++; 12 } Alternative if-else syntax: 1 x=(n>10)?0:1; //If n>10 then assign x=0 otherwise x=1;

15 Flow Control: if, else, switch, case, default, break if, if-else, else syntax: 1 int m=0, n=0; if (m<0) //Condition 4 { 5 n--; //n=n-1 6 } 7 else if (m>0) 8 { 9 n++; //n=n+1 10 } 11 else 12 { 13 n=0; 14 }

16 Flow Control: Relational Operations Relational less than/less than or equal to: <, <= Relational greater than/greater than or equal to: >, >= 1 float x=0.0, y=0.0, z=0.0; 2...//Code that modifies x,y,z values 3 if (x>=y) 4 { 5... //Do something 6 } 7 else if ((x<y)&&(x<=z)) 8 { 9... //Do something else 10 } 11 else //Otherwise do this else

17 Flow Control: Logical Operations Logical EQUAL: == 1 int n; 2...//Code that modifies the value of n 3 if (n==0) 4 { 5... //Do something 6 } Logical NOT:!= 1 int n; 2...//Code that modifies the value of n 3 if (n!=0) 4 { 5... //Do something 6 }

18 Flow Control: Logical Operations (Cont.) Logical AND: && 1 float x=0.0, y=0.0, z=0.0; 2...//Code that modifies x,y,z values 3 if ((x<y)&&(y<z)) 4 { 5... //Do something 6 } Logical OR: 1 float x=0.0, y=0.0, z=0.0; 2...//Code that modifies x,y,z values 3 if ((x>=y) (y<=z)) 4 { 5... //Do something 6 }

19 Flow Control: if, else, switch, case, default, break 1 unsigned day; 2...//Code that modifies the value of day 3 switch (day) { 4 case 1: 5 case 2: 6 case 4: 7 case 5: 8 printf("study hard\n"); 9 break; 10 case 3: 11 printf("study until 12:00am, go to gym\n"); 12 break; 13 case 6: 14 case 7: 15 printf("relax\n"); 16 break; 17 default: 18 printf("study hard\n"); 19 break; 20 }

20 Useful I/O Functions: printf syntax (1) 1 char ch="x"; 2 float pi= ; 3 int m=10; printf("the value of ch = %c \n",ch); 6 printf("the value of pi = %g \n",pi); 7 printf("the value of m = %d \n",m); Placeholder anatomy: %[Modifier][Width][.Precision]Type Type Variable Type Example %c char x %d signed integer -10 %u unsigned integer %hu unsigned short integer 2 %f float 3.14 %e or %E float scientific notation 3.14e0 or 3.14E0 %x or %X hexadecimal integer deaf or DEAF %o octal integer 377

21 Useful I/O Functions: printf syntax (2) Modifier Description 0 Pads the conversion on the left with zeros - The conversion is left-aligned within the display width + Forces to display a sign (+ or -) space Adds a space in front of positive numbers

22 Review Exercise 1 Write a small program to compute the following values: cos( 2π 3 ), sin(π 8 ), cos 1 (0.5), tan 1 ( π 2 ) Solutions: , , , Hint: include the <math.h> header and compile using: gcc revex1.c -o revex1.exe -lm

23 Review Exercise 2 Write a small program to compute the roots of a quadratic polynomial: ax 2 + bx + c = 0 Algorithm: 1 Compute first the discriminant D = b 2 4ac 2 If D is positive, there are two real-valued roots: x 1 = b + D, x 2 = b D 2a 2a 3 If D is zero, there is a double real-valued root: x 1 = x 2 = b 2a 4 If D is negative, there are two complex-valued roots: x 1 = b D 2a + j b D, x2 = 2a 2a j 2a Hint: For the complex solution split and print the solution in real and imaginary parts. Test your program with: a = 2, b = 3 and c = 1. a = 1, b = 6 and c = 9. a = 2, b = 3 and c = 5.