Keil uVision 4 is an integrated development environment (IDE) for embedded systems based on Arm microcontrollers. It provides project management, code editing, debugging, and simulation features. Keil uVision 4 is no longer available for download from the official website, but you can still find it on some third-party sources. Here are the steps to download and install Keil uVision 4 for free:

1. Go to https://keil-vision.software.informer.com/4.0/ and click on the “Download” button. This will redirect you to another page where you can choose a mirror site to download the setup file.
2. Once the download is complete, run the setup file and follow the instructions to install Keil uVision 4 on your computer. You may need to enter a license key during the installation process. You can use the following key: C51-9.01A-AXPHX-TEC51
3. After the installation is finished, launch Keil uVision 4 from your desktop or start menu. You can now create and manage your projects, edit your code, debug your programs, and simulate your devices using Keil uVision 4.

If you want to learn more about Keil uVision 4 and its features, you can refer to the documentation at https://developer.arm.com/documentation/101407/latest/User-Interface/uVision-GUI. You can also find example projects and utilities at https://www.keil.com/download/.

Keil uVision 4 is compatible with Windows XP, Vista, 7, 8, and 10. It supports a wide range of Arm microcontrollers from various vendors, such as STMicroelectronics, NXP, Texas Instruments, and more. You can use Keil uVision 4 to develop applications for various domains, such as automotive, industrial, medical, and IoT.

Keil uVision 4 has a user-friendly graphical user interface (GUI) that allows you to easily access all the tools and features. You can create and organize your projects using the Project Manager, which supports multiple targets and configurations. You can edit your code using the Source Editor, which supports syntax highlighting, code completion, and code folding. You can debug your programs using the Debugger, which supports breakpoints, watchpoints, trace, and logic analyzer. You can simulate your devices using the Simulator, which supports peripherals, interrupts, and external signals.

Keil uVision 4 also integrates with other tools and software that can enhance your development process. For example, you can use the RTX Real-Time Operating System (RTOS) to create multitasking applications. You can use the MDK Middleware to add networking, storage, USB, graphics, and other functionalities to your applications. You can use the ULINK Debug Adaptors to connect your devices to Keil uVision 4 and perform in-circuit debugging and testing.