signed char

Documentation Index

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Technical Specifications

• Size: Guaranteed to be exactly 1 byte. The number of bits in this byte is defined by the CHAR_BIT macro in <limits.h> (universally 8 bits on modern architectures).
• Memory Representation: The Most Significant Bit (MSB) acts as the sign bit. Modern C implementations utilize two’s complement representation for negative values.
• Value Range:
  • The C Standard guarantees a minimum range of -127 to 127.
  • On standard 8-bit two’s complement systems, the exact range is -128 to 127.
  • These limits are exposed via the SCHAR_MIN and SCHAR_MAX macros in <limits.h>.

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Type Distinctness

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Syntax and Initialization

#include <stdio.h>
#include <limits.h>

int main(void) {
    // Declaration and initialization
    signed char a = 100;
    signed char b = -50;
    
    // Character literals are of type 'int' in C, but can be safely 
    // truncated into a signed char if within the representable range.
    signed char c = 'Z'; 

    // SCHAR_MIN and SCHAR_MAX define the architectural limits
    signed char min_limit = SCHAR_MIN;
    signed char max_limit = SCHAR_MAX;

    return 0;
}

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Format Specifiers and I/O

• printf and %hhd: Because printf is a variadic function, a signed char argument is subject to default argument promotions and is always passed as an int. In the format string %hhd, d is the conversion specifier for a signed decimal integer, and hh is the length modifier. The hh modifier instructs printf to take the promoted int argument and convert it back to a signed char before formatting.
• scanf and %hhd: To read a numeric value directly into a signed char variable, use %hhd. This correctly expects a pointer of type signed char *.
• The %c Conversion Specifier: The c conversion specifier is used for character data. While passing a signed char to printf("%c", val) is valid (due to promotion to int), using %c with scanf strictly requires a char * argument. Passing a pointer to a signed char (signed char *) to scanf with %c results in a pointer type mismatch and will generate compiler warnings (e.g., -Wformat).

signed char val = -120;

// printf takes the promoted int, and 'hh' converts it back to signed char
printf("Integer value: %hhd\n", val);

// scanf requires the exact length modifier 'hh' and conversion specifier 'd'
// to safely write to a signed char pointer
scanf("%hhd", &val);

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Integer Promotion

signed char x = 100;
signed char y = 50;

// x and y are promoted to int before addition.
// The result (150) fits in an int, preventing overflow during the operation.
int result = x + y;