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int8 is a built-in primitive data type in Go that represents a signed 8-bit integer. It allocates exactly one byte of memory and uses two’s complement binary representation to store both positive and negative whole numbers. Technical Specifications
  • Size: 8 bits (1 byte)
  • Range: -128 to 127 (−27-2^7 to 27−12^7 - 1)
  • Zero Value: 0
  • Sign Bit: The Most Significant Bit (MSB) determines the sign (0 for positive, 1 for negative).
  • Package Constants: math.MinInt8 (-128) and math.MaxInt8 (127)

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Declaration and Initialization

You can declare an int8 using standard variable declaration syntax. If the type is not explicitly declared, Go will default to int for whole numbers, so the int8 type must be explicitly stated. 
package main

import "fmt"

func main() {
    // Explicit declaration with initialization
    var a int8 = 127
    
    // Declaration with zero value assignment
    var b int8
    
    // Short variable declaration with explicit type conversion
    c := int8(-128)
    
    fmt.Printf("%T: %d\n", a, a) // Output: int8: 127
    fmt.Printf("%T: %d\n", b, b) // Output: int8: 0
    fmt.Printf("%T: %d\n", c, c) // Output: int8: -128
}

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Strict Typing and Conversion

Go enforces strict type safety and does not perform implicit type coercion. An int8 cannot be directly operated on or compared with other integer types (like int, int16, or uint8) without explicit type conversion. 
package main

import "fmt"

func main() {
    var x int8 = 50
    var y int = 100

    // invalid operation: x + y (mismatched types int8 and int)
    // result := x + y 

    // Valid: Explicitly convert int8 to int
    result1 := int(x) + y 

    // Valid: Explicitly convert int to int8
    // Note: This will truncate if 'y' exceeds the int8 range
    result2 := x + int8(y) 
    
    fmt.Println(result1, result2) // Output: 150 150
}

​
Overflow and Underflow Behavior

Because int8 is constrained to 8 bits, exceeding its maximum or minimum boundaries results in arithmetic wraparound (overflow/underflow) based on two’s complement mechanics. Go does not panic on integer overflow during runtime. 
package main

import "fmt"

func main() {
    var max int8 = 127
    
    // Overflow: 01111111 (127) + 1 = 10000000 (-128)
    max++ 
    fmt.Println(max) // Output: -128

    var min int8 = -128
    
    // Underflow: 10000000 (-128) - 1 = 01111111 (127)
    min--
    fmt.Println(min) // Output: 127
}
Note: While runtime overflow wraps silently, compile-time overflow (e.g., var x int8 = 128) will trigger a compiler error: constant 128 overflows int8.
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