hi i m new to microcontrollers and i would like to know that when we make pins as output the IOH voltages are 5V and current is 60 microamp then how the high output can drive a 2SC1815 NPN Transitor base with a 10K Ohm resistor in series
Note that this is entirely a hardware question - nothing to do with Keil at all.
"when we make pins as output"
Classic 8051 pins are always "quasi-bidirectional" - you cannot "make them output"
See: " href= "www.8052.com/faqs.phtmlwww.8052.com/faqs.phtml
The Classic 8051 architecture is described in the so-called "bible" for the 8051:
Chapter 1 - 80C51 Family Architecture: www.nxp.com/.../80C51_FAM_ARCH_1.pdf
Chapter 2 - 80C51 Family Programmer's Guide and Instruction Set: www.nxp.com/.../80C51_FAM_PROG_GUIDE_1.pdf
Chapter 3 - 80C51 Family Hardware Description: www.nxp.com/.../80C51_FAM_HARDWARE_1.pdf
Note that some modern 8051-derivatives do have IO structures that can be configured for input, output, etc - for those you will have to refer to the Datasheet for the specific device.
Here are some other introductory & reference materials for the 8051: http://www.keil.com/books/8051books.asp www.8052.com/books.phtml www.8052.com/tutorial.phtml