CSI2172

Bjarne: Bjarne Stroustrup is the guy who invented C++ C++ means: “a C incremented”. It’s a clever way to say “C 2.0” If it works in C, it’s easy to make it work in C++

#include /* my first C program */ int main() { printf("Hello World\n"); return 0; } Start with C Library Function result. Typed Output Result

#include double func1(char, int); int func2(double, float); int main() { printf(“Value is %d”, func2(func1(‘a’, 2), 5.2f); return 0; } double func1(char a, int b){return a+b;} int func2(double a, float b){return a-b;}

The Tao of main() E There is one and only one main(…) E main(…) can be anywhere E All program begin where main(…) begins and end where main(…) ends E main(…) also returns

Variables: int a, b = 2; char x, y = 'a'; unsigned long int i1 = 0, i2 = 3; double pi = 3.14; double d = 5*pi;

Types : char int float double E char: 1 byte E int: signed integer E float: real number. 6 digits after decimal. E double: real number. 10 digits after decimal short, long signed, unsigned  Exemples: char (signed char), unsigned char, short int (signed short int), unsigned short int, int (signed int), unsigned int, long int (signed long int), unsigned long int, float, double, long double

More than you want to know about the int type int (default: signed short) short: 2 bytes (16 bits) signed: to unsigned: 0 to long: 4 bytes (32 bit) signed: to unsigned: 0 to In general: sizeof(short) <= sizeof(int) <= sizeof(long)

Some of my favorite chars char (default: signed) signed: -128 to 127 unsigned: 0 to 255 C '\a' keyboard bell C '\\' back slash C '\b' back space C '\?' question mark C '\f' form feed C '\n' new line C '\"' double quote C '\r' carriage return C '\t' horizontal tab C '\v' vertical tab C '\ooo' octal byte C '\xhh' hex byte C '\0' null byte

array int a[12]; //Array of 12 int char a[]; //Array of char, sized on initialization a = “hjah”; //” = short hand for NULL terminated array of chars, 5 elements float a[5][4]; //Matrix. Array of pointers Arrays are indexed from 0 to n-1 where n is the number of elements in the array /*INITIALISATION D'1 TABLEAU */ #define ROW 2 #define COLUMN 3 int main(){ int n[100], ctr; for(ctr = 0; ctr < 99; ctr++){ n[ctr] = 0; } int w[5] = {32, 21, 56, 32, 45}; char a[] = "Hello"; char b[6] = {'H','e','l','l','o','\0'}; int mat[ROW][COLUMN] = {{1,2}, {2,6}, {5,7}}; mat[0][2] = 3; }

strings H "a\tb" --> ab H "abcd\b\bx" --> abx H "\"hello world\"" --> "hello world" H "I don\'t know" --> I don't know H "hello\nworld" --> hello world H "\a" --> (rings the keyboard bell) There isn’t any string type in C. Strings are just arrays of char. Then there is just a bit of built-in syntactic sugar and some conventions. char [ ]; Examples: char name[20]; char firstName[20]; char sentence[300]; The last symbol is always '\0' (NULL). So for n characters, you need n+1 bytes.

/* Class example. Create an array of 11 chars, fill it with letters from ‘b’ to ‘j’ and print it to the output as a string */ char a[11]; a[10] = 'a'-'a'; for(int ctr=0; ctr < 10; ctr++){ a[ctr] = 'b'+ ctr; } printf("%s", a);

Decision,decision… if (...) stmt if (...) stmt1 else stmt2 if (...) { body } else { body } if (1)... true if (2)... true if (-1.5)... true if (0)... false int x = 2, y; if (x < 3) y = 5; else y = 4; The odd guy: cond ? e1 : e double x = n % 2 == 0 ? 4.3 : -2.3;

Branching(++): int x = 0, y = 0; switch(n) { case 1: case 2: x = 2; case 3: y = 3; break; case 4: x = 1; y = 4; case 5: x = 2; break; default: y = -1; }; nx y >5 0 -1

Repeat after me: for(e1;e2;e3)... int f=1, i; for(i=2; i<=n; ++i) f = f *i; for(;;)... while(cond)... int f=1, i=2; while(i <= n) f = f * i++; do body while(cond); int f=1, i = 1; do { f = f * i++; } while(i <= n);

Take me outta here break & continue int i, r = 0; for(i=0; i<n; ++i) { if (r % 2 == 0) continue; r += i; } int choice = 0; while(1) { choice = user_input(); if (choice 4) break; switch(choice) { case 1:...} goto(rare) void f() {... for(... ) { while(... ) {... if (wrong) goto error;... } for(... ) { if (wrong) goto error;... } }... error:...