Basically an array of characters that ends with the null terminator \0
String termination
Always ensure strings end with an null terminator\0, or you will encounter unexpected behaviour when using string methods.
In many cases, a string that is not properly terminated with \0 will result in illegal access of memory like Stack Overflow.
The issue shown in the picture can be resolved by assigning the string using double quotation marks - "apple", or, less preferably, by using str[5] = '\0';.
Boolean value of null terminator
The null terminator \0 has a boolean value of false which is equivalent to the integer 0!
Return length of string
Use strlen(s), \n is considered as a character.
String comparison
strcmp(s1, s2), it returns negative if s1 is lexicographically less than s2, positive if bigger, else both are equal.
We should use strncmp(s1, s2, n), because it safer, it will compare the first n characters if a null termination \0 is missing.
Assign string value in C
When we want to re-assign string value in C, we need to use strcpy(s1, s2) which assigns s2 to s1.
We should use strncpy(s1, s2, n), because it safer, it will only copy the first n characters if a null termination \0 is missing.
scanf()
The syntax is int scanf("%d", &a);
May have runtime crash
scanf()reads until the first whitespace, so the input may be too large and causes the program to crash.
The whitespace isn’t being read in.
fgets()
The syntax is char *fgets(char *str, int size, FILE *stream);
More reliable
fgets() reads until the first newline character or the specified size(size-1 chars) is reached, whichever comes first. So we can control how large the input will be; any excess will simply be ignored.
The \n is read in as one character.
Important
When we want to read in a string that should be null-terminated, but the string contains \n which prematurely terminates the fgets() function, we can use the following code snippet to ensure it is still null-terminated.
// Read a line of input from standard input (stdin) into the 'str' buffer, // with a maximum size of 'size' bytes.fgets(str, size, stdin);// Calculate the length of the string stored in 'str'.len = strlen (str);// Check if the last character in the string is a newline character ('\n'). // If so, replace it with a null terminator ('\0') to ensure proper null-termination.if (str[len-1] == '\n') str[len-1] = '\0';
puts()
Print a string to the console with newline included
C IO
Read float
scanf("%f", &miles); reads in a float number. The value it returns is the total number of successfully matched and assigned input items.
"%f" is known as a format string, &miles is known as a input list.
Print float
printf("That equals %9.3f km.\n", kms); prints a floating-point number to the screen, formatted to occupy a minimal width of 9 characters (including the decimal point and any padding spaces if the number is shorter). The number will be displayed with 3 decimal places of precision.
"That equals %9.3f km.\n" is known as a format string, kms is known as print list. \n is known as escape sequence to format the string.
