Practical C Programming - Chapter 5

Arrays, Qualifiers, and Reading Numbers

Strings

C does not allow one array to be assigned to another.

char sam[4];sam = "sam"; // error

The standard function fgets can be used to read a string from the keyboard. fgets includes the end-of-line in the string.

fgets(name, sizeof(name), stdin);

Multidimensional Arrays

int matrix[2][4];matrix[1][2] = 10;

Reading Numbers

scanf provides a simple and easy way of reading numbers that almost never work. The function scanf is notorious for its poor end-of-line handling, which makes scanf useless for all but an expert.

LOL

Instead, we use fgets to read a line of input and sscanf to convert the text into numbers. (The name sscanf stands for “string scanf”. sscanf is like scanf, but works on strings instead of the standard input.)

#include <stdio.h>char line[100]; /* line of input data */int height; /* the height of the triangle */int width;  /* the width of the triangle */int area;   /* area of the triangle (computed) */int main(){    printf("Enter width height? ");    fgets(line, sizeof(line), stdin);    sscanf(line, "%d %d", &width, &height);    area = (width * height) / 2;    printf("The area is %d\n", area);    return (0);}

Initializing Variables

C allows variables to be initialized in the declaration statement.

int counter = 0;int code[3] = {0, 1, 2};/*if an insufficient amount of numbers are present, C will initialize the extra elements to zero.*/int another_code[3] = {0}; /*if no dimension is given, C will determine the dimension from the number of elements in the initialization list.*/int some_code[] = {1,2,3,4,5};int matrix[2][4] =   {    {1,2,3,4},    {10,20,30,40}  }// stringschar name[] = {'S','a','m','\0'};// orchar name[] = "Sam";// orchar name[50] = "Sam";// which is equivalent tochar name[50];strcpy(name, "Sam");

Types of intergers

The long qualifier informs C that we wish to allocate extra storage for the integer. If we are going to use small numbers and wish to reduce storage, we use the qualifier short.

• int
• long
• short
• signed
• unsigned

signed long int number;

All int declarations default to signed. On the contrary, char declarations do not default to signed, the default is compiler dependent.

Types of Floats

• float
• double
• long double

The qualifier long double denotes extended precision. On some systems, this is the same as double; on others, it offers additional precision. All types of floating -point numbers are always signed.

Hexadecimal and Octal Constants

Base 10 Base 8 Base 16 6 06 0x6 9 011 0x9 15 017 0xF