What type of software is needed to draft sewing patterns?

I would say I'm a intermediate sewer and I would like to learn more on making my own patterns to sell. for example a dress, handbag, clothing etc.Weather I need software or not? When I buy patterns online, say..etsy or you can make this.com... most patterns are professional looking with straight, curved... computerized lines. How can i do the same? Do I need to have a software program? if so, what is it called? whats would be the appreciate name? I also have a mac computer. Thanks