The MCS BASIC–52 interpreter, developed by Intel, is still very popular, but in its 15th year it needs a thoroughgoing facelift.The MCS BASIC–52 V1.0 interpreter was specially developed by Intel in 1985 for the 8052-AH microcontroller. With its code size of only 8 kB, it fitted into the internal ROM storage of this controller. Unfortunately, the 8052-AH has gone out of production. Nonetheless, the interpreter still enjoys considerable popularity in its final ‘official’ version (1.1), in spite of a few errors. Nowadays, the 8052 family, with its many derivative versions, has become the most widely used microcontroller family. Regrettably, MCS BASIC 1.1 will not run directly on the fastest members of this family. The authors have made numerous modifications to the source code to arrive at version 1.3, with the following results:– The interpreter no longer has any known errors.– BASIC–52 V1.3 can program EEPROMs, even if they are located in external memory.– The new command ‘ERASE’ erases an EEPROM.– The maximum value for ‘XTAL’ can now be set as high as 78 MHz, so the interpreter can even run on a Dallas 80C320 at 33 MHz!– A new reset routine recognises the baud rate and various types of controllers. This means that BASIC–52 V1.3 can run on many 8052-family members (80616, 517(A), 528, 535, 537, 575 etc.).– The new OPCODE 43h reads a value from the argument stack into a variable.– The size of the interpreter is still only 8 kB, which means that it will fit into an 87C52 with 8 kB of internal EPROM.