set-frame-size

set-frame-size is a built-in function in `C source code'.

(set-frame-size FRAME WIDTH HEIGHT &optional PIXELWISE)

Set size of FRAME to WIDTH by HEIGHT, measured in characters.
Optional argument PIXELWISE non-nil means to measure in pixels. Note:
When `frame-resize-pixelwise' is nil, some window managers may refuse to
honor a WIDTH that is not an integer multiple of the default frame font
width or a HEIGHT that is not an integer multiple of the default frame
font height.