Computer is electronic device intended to accept data, perform prescribed precise and logical operations at high speed, and display the results of these operations. Types of computers include Mainframes, desktop, laptop, tablets, and smartphones. It consist of hard and soft drive.This over 410 pages publication, covers data for both beginners and advance levels of Microsoft, word, power Point, Excel and Access, the protection against computers’ attack, function of components, operating system, CPU, motherboard and the internet. In addition there are 310 self test questions and answers to these questions.There are many types of attack/courses which affect efficiency of computer which include Virus, Worms. Bandwidth. Trojan, Malware. Adware. Spyware, Grayware. Phishing. Span, Pop up. SYN Flood. Spoofing, Replay attack. DNS. DoS (Denial of Service), DDoS. Email bomb. PING OF DEATH pop up.There are many ways to protect computer include; Anti-spyware. Password protection. Login Username. Event logging. Asymmetric encryption SHA and MD5, Physical Human The VPN. TCP/IP or OSI. ActiveX., Java scrip. Back up, There are different type of backup.Incremental backup. Daily backup. Copy Backup. Backup passwordOnline backup. File system.FAT32. NTFS. Signature files. Mirrors. Security settings. Files permission, Modify files stop. Read only, Wireless security. WEPSSID. Accounts. Fire wall, Fire wall modes. packets inspection, Hardware firewall. Software firewall, Manual setting.Always visit the manufacture website to read about the type of computer suitable for your need.