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Objective-C is an object-oriented language that adds Smalltalk-style messaging on top of C. For decades it was the primary language for Apple's macOS and iOS development, built around classes, message sending with bracket syntax, and a dynamic runtime. It remains widely used in legacy Apple frameworks and interoperates cleanly with C and C++ code in mixed-language projects.
On CompileBytes, Objective-C programs are compiled with GCC (reported as version 12.2.0) rather than Apple's Clang, so platform-specific Cocoa frameworks like UIKit and Foundation may be unavailable. Plain C-style programs and basic Objective-C class definitions using the GNUstep runtime work well, making it suitable for learning the messaging syntax, memory model, and core language concepts without a Mac.
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main.m imports a header containing a small inline C-compatible helper.
#import <stdio.h>
#import "helper.h"
int main(void) {
printf("%d\n", answer());
return 0;
}
#ifndef HELPER_H
#define HELPER_H
static inline int answer(void) { return 42; }
#endif
#import <stdio.h>
int main(void) {
printf("Hello, World!\n");
return 0;
}#import <objc/Object.h>
#import <stdio.h>
@interface Greeter : Object
- (void)greet:(const char *)name;
@end
@implementation Greeter
- (void)greet:(const char *)name {
printf("Hello, %s!\n", name);
}
@end
int main(void) {
Greeter *g = [Greeter new];
[g greet:"CompileBytes"];
return 0;
}#import <stdio.h>
long factorial(int n) {
return n <= 1 ? 1 : n * factorial(n - 1);
}
int main(void) {
for (int i = 1; i <= 5; i++) {
printf("%d! = %ld\n", i, factorial(i));
}
return 0;
}#import <stdio.h>
int main(void) {
char name[64];
printf("Enter your name: ");
if (scanf("%63s", name) == 1) {
printf("Hi, %s!\n", name);
}
return 0;
}#import <objc/Object.h>
#import <stdio.h>
@interface Calc : Object
- (int)add:(int)a to:(int)b;
@end
@implementation Calc
- (int)add:(int)a to:(int)b {
return a + b;
}
@end
int main(void) {
Calc *c = [Calc new];
printf("sum = %d\n", [c add:3 to:4]);
return 0;
}#import <stdio.h>
typedef struct {
int x;
int y;
} Point;
int main(void) {
Point p = {3, 4};
Point *ptr = &p;
printf("(%d, %d)\n", ptr->x, ptr->y);
return 0;
}#import <objc/Object.h>
#import <stdio.h>
@interface Counter : Object
{
int value;
}
- (void)increment;
- (int)value;
@end
@implementation Counter
- (void)increment { value++; }
- (int)value { return value; }
@end
int main(void) {
Counter *c = [Counter new];
[c increment];
[c increment];
printf("count = %d\n", [c value]);
return 0;
}#import <stdio.h>
int main(void) {
int nums[5] = {1, 2, 3, 4, 5};
int sum = 0;
for (int i = 0; i < 5; i++) {
sum += nums[i];
}
printf("sum = %d\n", sum);
return 0;
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Objective-C is one of 23 linked-project compilers. Run always starts main.m; selecting a helper tab changes what you edit, not the entry file.
main.m imports a header containing a small inline C-compatible helper.
Linked-project languages (23): Node.js, TypeScript, Deno, Python, C, Go, Dart, Swift, Rust, Ruby, PHP, Java, Kotlin, C++, C#, Nim, Crystal, Haxe, Zig, Scala, D, Bun, Objective-C.
Single-file scratchpads (46): Matplotlib, NumPy, pandas, Haskell, Clojure, Perl, Lua, Tcl, jq, Raku, Elixir, Bash, Zsh, Nushell, R, Assembly (NASM), Julia, Octave, Groovy, PowerShell, Visual Basic .NET, Odin, Pascal, Lisp, Erlang, CoffeeScript, COBOL, BASIC, V, Racket, OCaml, Prolog, AWK, Emacs Lisp, Emojicode, Forth, F#, Fortran, Assembly (NASM64), Solidity, Mojo, Ada, WASM (WAT), Gleam, Shell Script (sh), Scheme. Their extra project files are not submitted to the runtime.
Download project exports every Objective-C tab and a README in one ZIP archive.