CCleaner is a utility software designed to optimize computer performance by removing unnecessary files and entries. Here are the main features and functions of CCleaner:

1. Junk File Removal: CCleaner scans for and deletes temporary files, system caches, memory dumps, log files, and other unneeded files that accumulate over time and occupy disk space.
2. Registry Cleaner: It cleans the Windows Registry by removing unused and old registry entries, which can help improve system stability and performance.
3. Uninstall Programs: CCleaner offers an uninstaller tool to remove installed programs more thoroughly than the default Windows uninstaller.
4. Startup Management: It allows users to manage startup programs to improve boot time by disabling or removing unnecessary programs that run on startup.
5. Privacy Protection: CCleaner can erase browser history, cookies, and other tracking data to help protect user privacy.
6. Drive Wiper: It includes a tool to securely erase data from drives, ensuring that deleted files cannot be recovered.
7. Software Updater: This feature checks for updates to installed software, helping users keep their applications up-to-date.