# SDL_islower Report if a character is lower case. ## Header File Defined in [](https://github.com/libsdl-org/SDL/blob/main/include/SDL3/SDL_stdinc.h) ## Syntax ```c int SDL_islower(int x); ``` ## Function Parameters | | | | | --- | ----- | ------------------------- | | int | **x** | character value to check. | ## Return Value (int) Returns non-zero if x falls within the character class, zero otherwise. ## Remarks **WARNING**: Regardless of system locale, this will only treat ASCII values 'a' through 'z' as true. ## Thread Safety It is safe to call this function from any thread. ## Version This function is available since SDL 3.2.0. ---- [CategoryAPI](CategoryAPI), [CategoryAPIFunction](CategoryAPIFunction), [CategoryStdinc](CategoryStdinc)