CS/COE 1520 pitt.edu/~ach54/cs1520 C C Developed by Dennis - - PowerPoint PPT Presentation

CS/COE 1520

pitt.edu/~ach54/cs1520

C

• Developed by Dennis Ritchie as a

language to build utilities for Unix

• Grew out of Ritchie’s work to improve

the B programming language

• The first C Compiler was included

with Version 2 Unix in 1972

• By Version 4 Unix, the kernel was

reimplemented in C

• Current version is C18

C

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#include <stdio.h> int main(void) { printf("hello, world\n"); }

Hello World

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#include <stdio.h> #include <stdlib.h> #include <time.h> int main(int argc, char **argv) { char str[25]; srand((unsigned) time(NULL)); unsigned int r = rand() % 100; while(r < 85) { if(r > 75) { printf("%u: so close!\n", r); } else if(r > 45) { printf("%u: Getting there...\n", r); } else { sprintf(str, "%u: Still so far away!\n", r); printf("%s", str); } r = rand() % 100; } printf("OUT!\n"); }

Basic Syntax

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• Unlike JavaScript and Python, C is statically typed
• However types can be cast from one type to another

Typing

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• char

○ Can be signed or unsigned

• int

○ Can be short or long ○ Can be signed or unsigned

• float
• double

○ Can be long

Basic Types

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• +
• *
• /
• %
• ++
• Numerical Operators

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• _Bool data type added in C99
• 0 is false
• 1 is true
• Any other value placed in the variable is stored as 1

Boolean Operators

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• Arrays are a collection of elements of the same type
• The size of the array is set when it is defined and it cannot be

a variable

○ float grades[50] ○ char hello[] = {‘H’, ‘e’, ‘l’, ‘l’, ‘o’} ○ int coords[10][10]

• To find the size of an array, you take the sizeof() the array

divided by the sizeof the data type

○ int helloSize = sizeof(hello)/sizeof(char)

Arrays

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• There is no string data type
• Strings are stored as char[]

○ char hello[12];

• Strings literals can be defined using “

○ strcpy(hello, “Hello World!”);

• String manipulation and examination is done with functions

○ strcpy ○ strcat ○ strlen ○ strcmp ○ ...

Strings

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• Nope

Structures

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• Very nope

Pointers

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• // Single line comment
• /*

Multiline comment */

Comments

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• <
• >
• <=
• >=
• ==
• !=

Comparison Operators

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• &&
• ||
• !

Logical Operators

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• =
• +=
• =
• *=
• /=
• %=

Assignment Operators

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if (r > 75) { //true statements } else if(r > 45) { //else if true } else { //false statements }

Selection Structures

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switch(x) { case val1: case val2: break; default: }

• while (condition) {

}

• do {

} while (condition)

• for(counter; condition; update counter) {

}

Loops

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int max(int a, int b) { if (a > b) { return a; } return b; } max(2,6);

Functions

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• Prints a formatted string to stdout
• printf(formatted string, var1, var2…)

○ Formatted string is a string literal with tags that start with % ■ Eg.

• %s for strings
• %d or %i for signed integers
• %u for unsigned integers

○ printf("%u: Getting there...\n", r);

• Sprintf is like printf except the resulting string is placed in a

variable

○ sprintf(str, "%u: Still so far away!\n", r);

Printf & sprintf

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• There is a lot more to C

○ Structures ○ Pointers ○ Enums ○ Unions ○ Function pointers ○ Inline functions ○ Bitwise operators ○ Inline assembly ○ ...

This was a brief introduction

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