Here in great detail how to prepare a 4* 4, the ranks of scanning keyboard (which has passed keil compiler and use). The program I use P1 as the ranks of scanning ports, it can identify whether a number of key press, whether the release button. Speaking for beginners is a good source

key
...\code
...\....\config.h
...\....\main.C
...\key
...\key.hex
...\key.lnp
...\key.M51
...\key.Opt
...\key.plg
...\key.Uv2
...\main.lst
...\main.obj
...\STARTUP.A51
...\STARTUP.LST
...\STARTUP.OBJ

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