What are the Unix system calls for Input and Output?

In Unix, the primary system calls for input and output are read(), write(), open(), close(), and lseek(). The open() call is used to open a file descriptor for reading or writing, while read() and write() perform the actual data transfer between the file descriptor and a buffer in memory. The close() call is used to close the file descriptor, and lseek() allows for repositioning the file pointer within the file. These calls provide a low-level interface for file and device I/O operations.