Add amount to a numeric variable (default 1). DEC subtracts instead.
INC var [, amount] DEC var [, amount]
var - numeric variable amount - value to add or subtract (optional; default 1)
Example:
A = 10
INC A
INC A, 2
PRINT A
Source: docs/help/inc.txt inmmcore. On the computer, typeHELP INC.