Question

the following shader is said to be one string and a null-terminated string.

A shader:

const GLchar* VertexShader =
{
    "#version 330\n"\

    "layout(location=0) in vec4 in_Position;\n"\
    "layout(location=1) in vec4 in_Color;\n"\
    "out vec4 ex_Color;\n"\

    "void main(void)\n"\
    "{\n"\
    "   gl_Position = in_Position;\n"\
    "   ex_Color = in_Color;\n"\
    "}\n"
};

My questions are:

1. What are the slashes mean at the end of each line? Moreover, why the last line doesn’t has a slash?
2. There are several strings in the shader, why the shader is said to have only one string?
3. Why it is said to be a null-terminated string? (Since there is no ‘\0’)

Answer 1

What are the slashes mean at the end of each line? Moreover, why the last line doesn’t has a slash?

It is a line continuation, it means the current line continues in the next one.

There are several strings in the shader, why the shader is said to have only one string?

Sequential string literals are collapsed into a single one. So "ab" "c" becomes "abc".

Why it is said to be a null-terminated string? (Since there is no ‘\0’)

String literals are null-terminated. So "ab" is actually {'a', 'b', '\0'}. Note that when string literals are collapsed, all but the last implicit null-termination characters are removed.