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
We don't even know if you are using a chip with 5V supply voltage. If you have a 3.3V part, then it will obviously not have any 5V to drive the pin with.
Anyway, the datasheet for the specific chip will contain all parameters needed to figure out how much current a pin can drive/sink and typical output voltages. There is no difference between a microcontroller and other digital chips in this regard.
Most microcontrollers are quite good at sinking current, allowing a LED to be connected (with suitable series resistor) between processor pin and VCC. Some microcontrollers are quite capable to drive the pin high, but a lot of them can supply a very marginal current and/or may depend on external pull-up resistors to keep the pin high. But once more - that information is available in the datasheet for the specific processor you are interested in.
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