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An Introduction to Red Hat Linux Course Contents of Red Hat Linux – 1. File and Directory Operations 2. User Information 3. File Permissions 4. Linux File System Essentials 5. X-Window System and GUI application (introduction) 6. Standard I/O Pipes 7. String Processing 8. Process 9. VI editor 10. Bash Shell and Shell Scripting 11. Basic Network Clients Introduction An operating system (OS) is software designed to act as an interface between the computer and the user. It performs various important functions such as , · An OS is a command interpreter. It translates the high level language to machine language and vice versa. · An OS acts as process manager. There are various processes running simultaneously in a computer. The amount of time to be spent on a process by the CPU is decided by the OS. · An OS is a memory manager. As said above, there are various processes

MIME Overview by Mark Grand Internet e-mail allows mail messages to be exchanged between users of computers around the world and occasionally beyond… to space shuttles. One of the main reasons that Internet e-mail has achieved such wide use is because it provides a standard mechanism for messages to be exchanged between over 1,000,000 computers connected to the Internet. The standards that are the basis for Internet e-mail were established in 1982. Though they were state of the art in 1982, in the intervening years they have begun to show their age. The 1982 standards allow for mail messages that contain a single human readable message with the restrictions that: • the message contains only ASCII characters. • the message contains no lines longer than 1000 characters. • the message does not exceed a certain length The 1982 standards do not allow EDI to be transmitted through Internet mail, since EDI messages can violate all of these restrictions. There are a number of other types of me

Primary key constraints This constraint avoids duplication of rows and does not allow NULL values, when enforced in a column or set of columns. A a result it is used to identify a row. A table can have only one primary key. If a primary key constraint is assigned to more than one column(i.e) or combination of columns it is said to be a composite primary key (or simply a composite key), which can contain a maximum of 16 columns. Primary key constraint cannot be defined in an alter table command when the table contains rows having NULL values. Run and Check your out put - select * from emp; - select deptno, dname, loc from dept; - select empno, ename, salary, hiredate from emp; - select ename,salary, salary+100 from emp; - select ename, salary, (salary*12)+100 from emp; - select ename,slary, (salary*12)+comm. from emp; - select ename,salary, (salary*12)+nvl(comm,0) from emp; - select ename “Full Name”, salary*12 “Annual Salary” from emp; - select enamejob from emp; - select ename’ is a ‘