Intensive Programming in Linux with C.F. Yurkoski - CS288

Cs288 Intensive Programming in Linux Instructor: C F Yurkoski Christopher.f.yurkoski@njit.edu Section web site: https://web.njit.edu/~yurkowsk/cs288.html Class 6 6-9-15 1

Topics today Homework revu More C Time for questions

text 6-9-15 cfy 3

Submit only .c files (or .h if I ask for header files too.) Insure that your code compliles on the afs Linux using the default options (no gcc) Write a hello world program done in class last week Do problem 1-4 from text Do problem 1-8 from text

First program /* This is a comment */ #include <stdio.h> /* preproc d*/ main() { printf("hello world\n"); } 6-9-15 5

Problem 1-4 Exercise 1 the corresponding Celsius to Fahrenheit table. Exercise 1- -4. 4. Write a program to print https://web.njit.edu/~yurkowsk/x/problem1-4.c

Problem 1-8: ite a program to count blanks, tabs, and newlines. ./public_html/x/exer1-8A.c

Some more Basics of C 6-9-15 10

Conditional Operator ? : exp1 ? exp2 : exp3 If exp1 is non-zero value of expression is exp2 otherwise it is exp3 1 ? 2 : 3 6-9-15 cfy 26

Operator Precedence left to right * / % + - 6-9-15 cfy 29

Some Basics /* Comments */ { blocks } Parameters ( ) # preprocessor directive Statements end with ; Loops: for while Conditionals if then 6-9-15 30

$ cat header.h #define ROOT 1 $ cat main1.c /* * This is a multi-line * comment block. */ #include <srdio.h> #include "header.h" /* This a one line comment */ main(){ int x=ROOT; /* this is an embeeded comment */ #ifdef ROOT printf("%d",x); #else printf("not root\n"); #endif }

$ cc main1.c $ ./a.out 1$

Basic printf formats %i or %d %c %f %s int char float string 6-9-15 cfy 33

Width and precision %d %6d %f %6f print as floating point, at least 6 characters wide %.2f print as floating point, 2 characters after decimal point print as decimal integer print as decimal integer, at least 6 characters wide print as floating point 6-9-15 cfy 34

I/O C=getchar(); putchar(C); 6-9-15 cfy 35

for statement for(init;condition;increment) { statement(s); } for(i=0;i<5;i++) { printf( %d\n ,i); } 6-9-15 cfy 36

Symbolic Contants #define name replacement text #define LIMIT 30 6-9-15 cfy 37

Escape sequences \a \b \f \n \r \t \v \\ \ \ \? \nnn any as an octal number \xhh a hexadecimal number 07 08 0C 0A 0D 09 0B 5C 27 22 3F Alarm (Beep, Bell) Backspace Formfeed Newline (Line Feed) Carriage Return Horizontal Tab Vertical Tab Backslash Single quotation mark Double quotation mark Question mark The character whose numerical value is given by nnn interpreted any The character whose numerical value is given by hh interpreted as 6-9-15 38

if statement if ( expression) statement else statement if ( expression ) statement else if ( expression ) statement 6-9-15 cfy 39

arrays int myarray[10]; 6-9-15 cfy 40

functions int function ( int param1, char param2); int function ( int param1, char param2) { int local1, local2; /* call by value */ retval=function2 (local1); } return(10); 6-9-15 cfy 41

argv, argc #include <stdio.h> int main (int argc, char *argv[]) { printf( %s\n ,argv[0]); return 0; } 6-9-15 cfy 42

compiler cc file.c o file 6-9-15 cfy 43

More basic C More on arrays: Array initialization during declaration: int num[5]; num[0]=1; int num[5]={1,2,3,4,5}; 6-9-15 cfy 44

Multi-dimensional arrays int a[2][3]; int a[2][3]={{1,2,3},{4,5,6}}; 6-9-15 cfy 45

Multi-dimensional arrays cont #include <stdio.h> main() { int a[2][3]={{1,2,3},{4,5,6}}; int i,j; for(i=0;i<2;i++) for(j=0;j<3;j++) } printf("a[%d][%d]=%d\n",i,j,a[i][j]); 6-9-15 cfy 46

Multi-dimensional arrays cont afsconnect1-58 >: ./a.out a[0][0]=1 a[0][1]=2 a[0][2]=3 a[1][0]=4 a[1][1]=5 a[1][2]=6 6-9-15 cfy 47

Strings are just arrays of characters. #include <stdio.h> main() { char name1[25]="NJIT"; char name2[25]={'N','J','I','T','\0'}; printf("name1=%s\n",name1); printf("name2=%s\n",name2); } >: ./a.out name1=NJIT name2=NJIT 6-9-15 cfy 48

Strings (cont). main() { char name1[25]="NJIT"; char name2[25]={'N','J','I','T','\0'}; char *name3="NJIT"; printf("name1=%s\n",name1); printf("name2=%s\n",name2); printf("name3=%s\n",name3); } afsconnect1-67 public_html >: ./a.out name1=NJIT name2=NJIT name3=NJIT 6-9-15 cfy 49

Strings (cont). Header file string.h Some examples: strcmp String Compare strcat String Concatenation memcpy Copy Memory Block strlen String Length 6-9-15 cfy 50

Strings (cont). General form: Strcat(string1,string2) Appends string2 to string1; 6-9-15 cfy 51

Addresses! & used to get the address of a variable main() { int i=666; printf("i= %d\n",i); printf("&i= %d\n",&i); } afsconnect1-72 public_html >: ./a.out i= 666 &i= 1814055836 6-9-15 cfy 52

More C keywords switch sizeof Storage classes: auto register extern static break, continue, goto 6-9-15 cfy 53

switch( Grade ) { case 'A' : printf( "Excellent\n" ); case 'B' : printf( "Good\n" ); case 'C' : printf( "OK\n" ); case 'D' : printf( "Mmmmm....\n" ); case 'F' : printf( "You must do better than this\n" ); default : printf( "What is your grade anyway?\n" ); } 6-9-15 cfy 54

label: while (true) { if(a) break; if(b) continue; if(c) goto label; } 6-9-15 cfy 55

main() { int i=666; char array[15]; double n; printf("sizeof i= %d\n",sizeof(i)); printf("sizeof array= %d\n", sizeof(array)); printf("sizeof n= %d\n", sizeof(n)); } >: ./a.out sizeof i= 4 sizeof array= 15 sizeof n= 8 6-9-15 cfy 56

static Has number of implications: Local static variables initialized only once and retain their value. Guaranteed to be automatically initialized to zero if not otherwise initialized. Global static variable inaccessible outside the file. Can be applied to functions. 6-9-15 cfy 57

Structures! struct <name> { element1; element2; } 6-9-15 cfy 58

Structures example struct class { char name[30]; int number; char instructor[25]; int students[35]; }; 6-9-15 cfy 59

Structures element dereferencing structure-variable.stucture-member; e.g.: x=class.number; 6-9-15 cfy 60

Arrays of Structures struct class semester[30]; struct grades { char name[30]; int id; int grades[10]; }g[35]; 6-9-15 cfy 61

Unions struct class semester[30]; union students { long x; char grades[8]; }g[35]; 6-9-15 cfy 62

sizeof can be applied to unions and structures Structures can be nested. 6-9-15 cfy 63

Pointers General form: datatype *ptrname; int x=666, y=555; Int *p; p = &x; y = *p; 6-9-15 cfy 64

Some cc command line options -I -L -c -o Compiling multiple C files. Linking multiple objects.