get_specified_input.c

#include <stdio.h>
#include <conio.h>
#include <math.h>
#include <string.h>

double getOnlyRealNumber();
double stringToDouble(char *);

long long int getOnlyInteger();
long long int stringToInt(char *);

int main()
{
    // Get Only Real Number
    printf("\nEnter A Real Number (Number With Decimal Point) => ");
    printf("\nEntered Real Number %lf", getOnlyRealNumber());

    // Get Only Integer
    printf("\n\nEnter An Integer => ");
    printf("\nEntered Integer => %lld", getOnlyInteger());

    getch();
    return 0;
}

double getOnlyRealNumber()
{
    char str[30];
    int i = 0;
    while (1)
    {
        char ch = getch();
        if (ch == ' ' || ch == 13)
            break;
        else if ((ch >= '0' && ch <= '9' || ch == '.') || ch == '-' && i == 0)
        {
            putch(ch);
            str[i] = ch;
            i++;
        }
        else if (ch == 8 && i > 0)
        {
            i--;
            putch('\b');
            putch(' ');
            putch('\b');
        }
    }
    str[i] = 0;
    return stringToDouble(str);
}

double stringToDouble(char *str)
{
    long long int integeralPart = 0, decimalPart = 0;
    int i = 0;
    if (str[0] == '-')
        i = 1;
    for (; str[i] != '.' && str[i]; i++)
        integeralPart = integeralPart * 10 + (str[i] - 48);

    if (strlen(str) != i)
    {
        for (i++; str[i]; i++)
            decimalPart = decimalPart * 10 + (str[i] - 48);
    }

    int countDigits = 0, copyDecimalPart = decimalPart;
    while (copyDecimalPart > 0)
    {
        countDigits++;
        copyDecimalPart /= 10;
    }
    double digitsAfterPoint = 0;
    if (countDigits)
        digitsAfterPoint = decimalPart / pow(10, countDigits);

    double num = integeralPart;
    num += digitsAfterPoint;
    if (str[0] == '-')
        num = -num;
    return num;
}

long long int getOnlyInteger()
{
    char str[30];
    int i = 0;
    while (1)
    {
        char ch = getch();
        if (ch == ' ' || ch == 13)
            break;
        else if (ch >= '0' && ch <= '9' || ch == '-' && i == 0)
        {
            putch(ch);
            str[i] = ch;
            i++;
        }
        else if (ch == 8 && i > 0)
        {
            i--;
            putch('\b');
            putch(' ');
            putch('\b');
        }
    }
    str[i] = 0;
    return (stringToInt(str));
}

long long int stringToInt(char *str)
{
    long long int integeralPart = 0;
    int i = 0;
    if (str[0] == '-')
        i = 1;
    for (; str[i]; i++)
        integeralPart = integeralPart * 10 + (str[i] - 48);

    if (str[0] == '-')
        integeralPart = -integeralPart;
    return integeralPart;
}