While most children his age sketch on paper with crayons, nine-year-old Lim Ding Wen from Singapore has a very different canvas, Reuters reports — his iPhone. Lim, who is in fourth grade, writes applications for Apple’s popular iPhone. His latest, a painting program called Doodle Kids, reportedly has been downloaded more than 4,000 times from Apple’s iTunes store in two weeks. The program lets iPhone users draw with their fingers by touching the iPhone’s touch screen and then clear the screen by shaking the phone. "I wrote the program for my younger sisters, who like to draw," Lim said. His sisters are aged 3 and 5. Lim, who is fluent in six programming languages, started using the computer at the age of 2. He has since completed about 20 programming projects…