Problem in C's programming concept for ucontroller

Sir,
I am frequent user of assembly language regarding MCS 51 family but now I want to shift on C programming I have understanding of C language. I am facing lot of difficulties in C for ucontroller programming.For assembly the instruction set is available is there any C's instruction set for controller to understand app notes of examples available in C. How can I use internal ram (bit addressable), rotate commands,interrupt vectors,serial interrupts, data pointer,bit checking.
How can I interpret these commands use in Keil examples? Is any help or guidance for me....?

LCD_DATA = (LCD_DATA&0x0F)|((value<<4)&0xF0);
SDA = (bit)((value&0x80) >> 7);
TMOD &= ~0xF0;
TMOD |= 0x20;