💾 String Manipulation functions in C without using Library

#include <stdio.h>

int StringLength(char *);
char *StringReverse(char *);
char *ToLowerCase(char *);
char *ToUpperCase(char *);
char *StringLeft(char *, int);
char *StringRight(char *, int);
char *StringMid(char *, int, int);
char *StringMid2(char *, int);

/*
    Some core level string manipulating functions written in C
    Created Date    : [1/26/2019]
    Modified Date   : [1/27/2019]
*/
void main() {

    printf("%s\n", "String Manipulations In C without using Library");
    printf("%s\n", "===============================================");
    printf("\n");

    char MyString[200];
    printf("Enter String: ");
    scanf("%[^\n]s", MyString); // allows all character but NewLine

    printf("\n");
    printf("Original : %s\n", MyString);
    printf("Length   : %d\n", StringLength(MyString));
    char* revString = StringReverse(MyString);
    printf("Reversed : %s\n", revString);
    printf("ToLower  : %s\n", ToLowerCase(MyString));
    printf("ToUpper  : %s\n", ToUpperCase(MyString));
    printf("Left(0)  : %s\n", StringLeft(MyString, 0));
    printf("Left(4)  : %s\n", StringLeft(MyString, 4));
    printf("Left(99) : %s\n", StringLeft(MyString, 99));
    printf("Right(0) : %s\n", StringRight(MyString, 0));
    printf("Right(7) : %s\n", StringRight(MyString, 7));
    printf("Right(99): %s\n", StringRight(MyString, 100));
    printf("Mid(3,5) : %s\n", StringMid(MyString, 3, 5));
    printf("Mid(8)   : %s\n", StringMid2(MyString, 8));
    printf("\nEnd of the Program!");
}

/* Function to find the length of the given string*/
int StringLength(char *InStr) {
    int i = 0;
    while (InStr[i++] != '\0');
    return --i;
}

/* Function that reserve the given string*/
char* StringReverse(char *InStr) {

    int len = StringLength(InStr);

    //Dynamic memory allocation
    char *OutStr = malloc(sizeof(char) * (len));

    int index = 0;
    while (len > 0) {
        OutStr[index++] = InStr[--len];
        //printf_s("%d %d %s\n", len, index, OutStr);
    }

    OutStr[index] = '\0';   // Safe Measure
    return OutStr;
}

/* Function that converts the given string to lowercase characters*/
char* ToLowerCase(char *InStr) {

    int len = StringLength(InStr);

    //Dynamic memory allocation
    char *OutStr = malloc(sizeof(char) * (len));

    int index = 0;
    while (InStr[index] != '\0') {
        char letter = InStr[index];
        if ((letter >= 'A') && (letter <= 'Z')) // A:65, Z:90
            letter = letter + 32;
        OutStr[index++] = letter;
    }

    OutStr[index] = '\0';
    return OutStr;
}

/* Function that converts the given string to uppercase characters*/
char* ToUpperCase(char *InStr) {

    int len = StringLength(InStr);

    //Dynamic memory allocation
    char *OutStr = malloc(sizeof(char) * (len));

    int index = 0;
    while (InStr[index] != '\0') {
        char letter = InStr[index];
        if ((letter >= 'a') && (letter <= 'z')) // a:97, z:122
            letter = letter - 32;
        OutStr[index++] = letter;
    }

    OutStr[index] = '\0';
    return OutStr;
}

/* Function that extracts given N characters from the given string starting from left*/
char* StringLeft(char *InStr, int n) {

    if (n <= 0) n = 0;

    int len = StringLength(InStr);
    if (n >= len) n = len;

    //Dynamic memory allocation
    char *OutStr = malloc(sizeof(char) * (n));

    int index = 0;
    while (n > 0) {
        OutStr[index] = InStr[index];
        index++;
        n--;
    }

    OutStr[index] = '\0';
    return OutStr;
}

/* Function that extracts given N characters from the given string starting from right*/
char* StringRight(char *InStr, int n) {

    if (n <= 0) n = 0;

    int len = StringLength(InStr);
    if (n >= len) n = len;

    //Dynamic memory allocation
    char *OutStr = malloc(sizeof(char) * (n));

    int index = 0;
    while (n > 0) {
        OutStr[index] = InStr[len - n];
        index++;
        n--;
    }

    OutStr[index] = '\0';
    return OutStr;
}

/* Function that extracts given N characters from the given string starting from start position*/
char* StringMid(char *InStr, int start, int n) {

    if (n <= 0) n = 0;
    if (start <= 0) start = 1;

    int len = StringLength(InStr);
    if (n >= len) n = len;

    //Dynamic memory allocation
    char *OutStr = malloc(sizeof(char) * (n));

    int index = 0;
    while (n > 0) {
        OutStr[index] = InStr[(start - 1) + index];
        index++;
        n--;
    }

    OutStr[index] = '\0';
    return OutStr;
}

/* Function that extracts characters from the given string starting from start position till end*/
char* StringMid2(char *InStr, int start) {

    int len = StringLength(InStr);
    int n = len - start;

    if (start <= 0) {
        start = 1;
        n = len;
    }

    //Dynamic memory allocation
    char *OutStr = malloc(sizeof(char) * (n));

    int index = 0;
    while (n >= 0) {
        OutStr[index] = InStr[(start - 1) + index];
        //printf_s("%d %d %s\n", len, index, OutStr);
        index++;
        n--;
    }

    OutStr[index] = '\0';
    return OutStr;
}