关于 OpenGL shader language 的问题

如一下GLSL代码

• layout (location = 0) in vec3 position;
• void main() {
• gl_Position = vec4(position.x, position.y, position.z, 1.0);
• } layout (location = 0) in vec3 position; 这句是什么意思? gl_Position = vec4(position.x, position.y, position.z, 1.0); 这句中的 最后一个数 1.0 代表着什么

第一次来CSDN, 望诸位帮帮忙

装 CPAN安装，都安装了，再次安装提示安装是最新，但是check的时候就是提示not found。看google说这个因为安装文件位置不一致，求解呀 折腾了1天了

Chart: /usr/bin/perl install-module.pl Chart::Lines
Template-GD: /usr/bin/perl install-module.pl Template::Plugin::GD::Image
[root@localhost Bugzilla]# perl install-module.pl --all
Checking for CPAN (v1.81) ok: found v1.9800
Checking for YAML (any) ok: found v1.15
Checking for ExtUtils-MakeMaker (v6.31) ok: found v6.68
Reading '/root/.cpan/Metadata'
Database was generated on Fri, 17 Jun 2016 20:17:02 GMT
Installing Chart::Lines version 2.004010...
Chart::Lines is up to date (2.4.10).
Installing Template::Plugin::GD::Image version 1.56...
Template::Plugin::GD::Image is up to date (1.56).
Installing GD::Text version 0.86...
GD::Text is up to date (0.86).