While installing turbo c it asks "insert disk #1 into drive c".. what does it mean?. how can I install turbo c?

This is a guess, but when I've encountered messages like this in the past it was usually due to having copied the installer files for a program from their original floppy based distribution onto a hard drive and installing from the hard drive. The program's installer is expecting a disk change to occur to the next disk. Normally, hitting enter or whatever the continue key is for the installation would allow the install to progress as long as all the files are there. If the original floppy disks had files with the same names, it may be necessary to make separate directories for each original disk file set and an install directory and then copy each disk directory over into the install directory when required as the installation progresses. Can also use the DOS command prompt SUBST command to achieve the same effect.