If you don't need much brightness in your LED 7-seg display, you can use common anode displays and multiplex the voltage applied to the common anodes (4 PNP transistors and 8 resistors, or better 4 P-channel MOS transistors alone).

All the segments (cathodes) with the same name (a, b, ...) linked to a micro output via a common resistor (7 outputs). The AT98C2051 outputs can drive (sink) a LED directly, though the multiplexed operation will decrease the brightness.

A total of 11 lines must be employed using this approach, and the 2051 has only 15 lines. Only 4 spare lines for counting and maybe to establish a communication via the serial port.

In addition you will learn much more about 8051 programming with the SW option!.