C librarys

please Help I have some problem with C librarys under Linux not all libbrarys existed in the Linux (RH6.1) programs what work under DOS not work in Linux i get message "libname.h not found " some DOS C librarys was copied in directory "include" but some from them as "stdlib.h" "time.h" not work propearly and "dos.h" "conio.h" are work please say me where i can get Linux version of the are librarys glibc 2.1.13 installed Thanks