When you run this: PUBLIC SUB Main() DIM bByte AS Byte PRINT Bin(bByte, 8) BSet(bByte, 0) PRINT Bin(bByte, 8) BChg(bByte, 0) PRINT Bin(bByte, 8) bByte = bByte OR &H1 PRINT Bin(bByte, 8) PRINT BTst(bByte, 0) END You get this: 00000000 00000000 00000000 00000001 True BSet and BChg seem to do nothing... BTst works Gambas 2.22 Regards, Ron_2nd.